Df Quotes

We've searched our database for all the quotes and captions related to Df. Here they are! All 100 of them:

That’s the gist of it. Everyone wants to believe in God, but when He does show up and starts talking to people, everyone calls them crazy.
D.F. Noble
had to say over and over to myself, ‘Give up the drink or lose your soul! Give up the drink or break Polly’s heart!’ But thanks be to God, and my dear wife, my chains were broken, and now for ten years I have not tasted a drop, and never wish for it.
Anna Sewell (Black Beauty (DF Children's Classics Book 7))
¿Que es la maquinaria del PRI? Es el gobernador que manda a los maestros a marchar al DF para desquiciarla.
Denise Dresser
One day, I watched the sun setting forty-four times,’ you told me. And a little later, you added: ‘You know… when one is so terribly sad, one loves sunsets…’ ‘The day you watched those forty-four sunsets, were you that sad?’ I asked. But the little prince made no reply.
Antoine de Saint-Exupéry (The Little Prince)
Vicious, visceral visuals -Craig Mullins- brings Lovecraftian landscapes and beasts to life like a high powered blotter acid death ray.
D.F. Noble
I heard the stories of the storytellers, telling the stories people wanted to hear. Everyone finds the narrative that matches the narrative they already know and want. It wasn't that I didn't want to share the truth. It wasn't that I feared the response. It was that I no longer believed in a truth.
D.F. Lovett (The Moonborn)
Altering the course of rivers and moving mountains is easy. Changing someone’s character is impossible. Chinese saying
D.F. Swaab (We Are Our Brains: A Neurobiography of the Brain, from the Womb to Alzheimer's)
We drink water that once came from rivers. It leaves our bodies as urine, is purified, travels to the sea, evaporates, and then returns to our taps via rain and rivers.
D.F. Swaab (We Are Our Brains: A Neurobiography of the Brain, from the Womb to Alzheimer's)
Pre-birth exposure to nicotine or amphetamines also increases the likelihood of lesbian daughters.
D.F. Swaab (We Are Our Brains: A Neurobiography of the Brain, from the Womb to Alzheimer's)
A child with BIID cut dolls out of a magazine and then snipped off the leg that he himself didn’t want.
D.F. Swaab (We Are Our Brains: A Neurobiography of the Brain, from the Womb to Alzheimer's)
It is curious that a genetic predisposition for homosexuality should persist in populations over the course of evolution, given that this group reproduces so much less.
D.F. Swaab (We Are Our Brains: A Neurobiography of the Brain, from the Womb to Alzheimer's)
EEG measurements in newborns show a difference between the response to touch and the response to the pain of a heel prick only as of thirty-five to thirty-seven weeks.
D.F. Swaab (We Are Our Brains: A Neurobiography of the Brain, from the Womb to Alzheimer's)
In hospitals in the 1960s, alcohol was routinely administered intravenously to women at risk of giving birth prematurely.
D.F. Swaab (We Are Our Brains: A Neurobiography of the Brain, from the Womb to Alzheimer's)
Kermit “Late Term” Lector. “Good evening, Clarice,
D.F. Noble (Zombie! Zombie! Brain Bang!)
In addition, you’re more at risk of developing schizophrenia if you were born in the winter or if your mother was exposed to flu during the sixth month of pregnancy.
D.F. Swaab (We Are Our Brains: A Neurobiography of the Brain, from the Womb to Alzheimer's)
The functioning of the prefrontal cortex is inhibited by alcohol, which can lead to sudden, mindless violence after a night out.
D.F. Swaab (We Are Our Brains: A Neurobiography of the Brain, from the Womb to Alzheimer's)
Be nice to your kids, they’ll choose your nursing home. Text on a mug my daughter gave me
D.F. Swaab (We Are Our Brains: A Neurobiography of the Brain, from the Womb to Alzheimer's)
These hormonal extracts, which probably come from Russia, are sometimes still found in gyms, where they are used by bodybuilders who want to increase muscle mass.
D.F. Swaab (We Are Our Brains: A Neurobiography of the Brain, from the Womb to Alzheimer's)
Whether abuse as a child is a causal factor in the development of pedophilia in adulthood, or whether there’s a genetic factor in such families, still needs to be investigated.
D.F. Swaab (We Are Our Brains: A Neurobiography of the Brain, from the Womb to Alzheimer's)
The PFC plays a central role in regulating other brain areas and is responsible, among other things, for the control of our impulses, complex actions, planning, and organization.
D.F. Swaab (We Are Our Brains: A Neurobiography of the Brain, from the Womb to Alzheimer's)
A big complicated mess is easy. Making something simple and clear is hard.
D.F. Lamont
a la pobreza se le pega donde más le duele, tirando al aire lo poco que se tiene en la bolsa.
Guillermo Fadanelli (Hotel DF)
No matter what country he fights for, a wounded soldier on a battlefield will always call for his mother, not his father.
D.F. Swaab (We Are Our Brains: A Neurobiography of the Brain, from the Womb to Alzheimer's)
Grown-ups never understand anything by themselves and it is rather tedious for children to have to explain things to them time and again.
Antoine de Saint-Exupéry (The Little Prince)
completely thunderstruck.
Antoine de Saint-Exupéry (The Little Prince)
softly and gravely:
Antoine de Saint-Exupéry (The Little Prince)
Perhaps I am a little like grown-ups. I am getting old.
Antoine de Saint-Exupéry (The Little Prince)
I see the same sky above me, the same stars and moon, but nothing will ever be the same for me, because I love you.” Whoever said love was grand evidently had never been in love.
D.F. Jones (Ruby's Choice (Ditch Lane Diaries #1))
Maxey? Do you believe in ghosts?
D.F. Jones (Antique Mirror: A Witches of Hant Hollow short story (The Witches of Hant Hollow))
Tori jumped up and shouted, “What? This can’t be real! I don’t believe this! I can't be stuck here. I have a life, a wonderful career that’s really taking off. I just adopted Jett.
D.F. Jones (Antique Mirror: A Witches of Hant Hollow short story (The Witches of Hant Hollow))
When a pregnant woman experiences stress, the brain of a female fetus will become more male and vice versa
D.F. Swaab (We Are Our Brains: A Neurobiography of the Brain, from the Womb to Alzheimer's)
judicial system has no tradition of researching the effectiveness of its punishments.
D.F. Swaab (We Are Our Brains: A Neurobiography of the Brain, from the Womb to Alzheimer's)
Once again, it was thanks to the sheep, for suddenly the little prince questioned me as if seized by a grave doubt: ‘It is true, is it not, that sheep eat little shrubs?
Antoine de Saint-Exupéry (The Little Prince)
But I must be forgiven for that. My friend never explained
Antoine de Saint-Exupéry (The Little Prince)
It is only with one’s heart that one can see clearly. What is essential is invisible to the eye.
Antoine de Saint-Exupéry (The Little Prince)
Men are five times more likely than women to commit a murder. Moreover, men murder a relative or acquaintance only in 20 percent of cases, as opposed to 60 percent of cases for women.
D.F. Swaab (We Are Our Brains: A Neurobiography of the Brain, from the Womb to Alzheimer's)
Cannabis affects the brain because brain cells themselves produce cannabis-like neurotransmitters. The first such compound to be identified was christened anandamide, ananda being Sanskrit for “bliss.” The proteins that transmit anandamide’s message to the brain, the receptors, are mainly located in the striatum (hence the blissful feeling) and in the cerebellum (hence the unsteady gait after taking marijuana), in the cerebral cortex (hence the problems with association, the fragmented thoughts and confusion), and in the hippocampus (hence the memory impairment). But there are no receptors in the brain stem areas that regulate blood pressure and breathing. That’s why it’s impossible to take an overdose of cannabis, as opposed to opiates.
D.F. Swaab (We Are Our Brains: A Neurobiography of the Brain, from the Womb to Alzheimer's)
Another woman with an epileptic focus in the cerebral cortex refused both medication and the option of an operation, as she enjoyed the feeling of orgasm that preceded her epileptic attacks.
D.F. Swaab (We Are Our Brains: A Neurobiography of the Brain, from the Womb to Alzheimer's)
Brain operations have also been performed on homosexual prisoners with a view to reducing their sentences if the treatment proved effective. Naturally, the men all said that it was effective.
D.F. Swaab (We Are Our Brains: A Neurobiography of the Brain, from the Womb to Alzheimer's)
Justine watched two azure moons traverse the sparkling smear of Wall stars. They were in very strange orbits. And moving impossibly fast – actually accelerating. ‘Oh my God,’ she gasped. The Raiel’s planet-sized DF machines were flying into new positions. ‘The Raiel are getting ready for the last fight,’ Ehasz said numbly. ‘If they lose, that monster will consume the whole galaxy.
Peter F. Hamilton (The Dreaming Void (Void, #1))
Take the myth that we use only 10 percent of our brains. You might well be forgiven for thinking this in the case of certain people, but I haven’t the faintest idea what prompted this crazy theory
D.F. Swaab (We Are Our Brains: A Neurobiography of the Brain, from the Womb to Alzheimer's)
Take the myth that we use only 10 percent of our brains. You might well be forgiven for thinking this in the case of certain people, but I haven’t the faintest idea what prompted this crazy theory.
D.F. Swaab (We Are Our Brains: A Neurobiography of the Brain, from the Womb to Alzheimer's)
Is that a nice thing to say to your mother? Oh, how true it is that it is sharper than a serpent’s tooth to have a thankless child.” “Is that a nice thing to say to your daughter?” said unrepentant Valancy.
L.M. Montgomery (The Blue Castle (DF Modern Classics Book 8))
Paternal age plays a role in autism, too: The syndrome occurs ten times more frequently in people born to fathers in their fifties than in those whose fathers were in their twenties when they were conceived.
D.F. Swaab (We Are Our Brains: A Neurobiography of the Brain, from the Womb to Alzheimer's)
Each day, I learnt something about the planet, about the little prince’s departure from it, about his journey. The information would come very slowly, following the course of the little prince’s thoughts. Thus
Antoine de Saint-Exupéry (The Little Prince)
It is not my fault. I had been discouraged by grown-ups in my career as a painter when I was six years old, and I hadn’t learnt to draw anything with the exception of boas from the outside and boas from the inside.
Antoine de Saint-Exupéry (The Little Prince)
As for Barney Snaith, the only crime he has been guilty of is living to himself and minding his own business. He can, it seems, get along without you. Which is an unpardonable sin, of course, in your little snobocracy.
L.M. Montgomery (The Blue Castle (DF Modern Classics Book 8))
The unborn child’s great sensitivity to melody might also explain why French babies cry with a rising intonation and German babies with a falling intonation, reflecting the different intonation contours of the two languages.
D.F. Swaab (We Are Our Brains: A Neurobiography of the Brain, from the Womb to Alzheimer's)
Children who are seriously neglected during their early development also have smaller brains (fig. 7); their intelligence and linguistic and fine motor control are permanently impaired, and they are impulsive and hyperactive.
D.F. Swaab (We Are Our Brains: A Neurobiography of the Brain, from the Womb to Alzheimer's)
Although tests show no significant difference in the moral choices made by atheists and believers, the Intelligent Design movement claims that moral behavior is unique to man and derives from religion, especially Christianity.
D.F. Swaab (We Are Our Brains: A Neurobiography of the Brain, from the Womb to Alzheimer's)
Then you shall judge yourself,’ answered the king. ‘That is the most difficult thing of all. It is far more difficult to judge oneself than to judge others. If you succeed in judging yourself rightly, then indeed you are very wise.
Antoine de Saint-Exupéry (The Little Prince)
The more older brothers a boy has, the greater the chance that he will be homosexual. This is due to a mother’s immune response to male substances produced by boy babies in the womb, a response that becomes stronger with each pregnancy.
D.F. Swaab (We Are Our Brains: A Neurobiography of the Brain, from the Womb to Alzheimer's)
Some gender-based differences in our behavior emerge so early on that they can only have arisen in the womb. As early as the first day after birth, girl babies prefer to look at faces, while boy babies prefer to look at mechanical moving objects.
D.F. Swaab (We Are Our Brains: A Neurobiography of the Brain, from the Womb to Alzheimer's)
The Silverbird was tracking the Raiel’s gas giant-sized DF spheres as they continued their flight across the star system. Gravity waves spilled out from them with astonishing force, distorting the orbits within the main asteroid rings. A couple of small moons caught in the backwash had also changed inclination. All nine of the DFs were heading in towards the small orange star which Centurion Station’s never-named planet was in orbit around. As the ship watched, the photosphere started to dim.
Peter F. Hamilton (The Temporal Void (Void #2))
So De Waal might do well to ask God if he could also curb our tendency to take our lead from charismatic alpha males. Not only might this prevent future genocides and cultural revolutions, it might also reduce the likelihood of another disaster caused by corporate greed.
D.F. Swaab (We Are Our Brains: A Neurobiography of the Brain, from the Womb to Alzheimer's)
It gets weirder than you think,” Fiona said and let this idea sink in before continuing. “Did you hear that crazy story on Sunday? About a black bear dragging some guy from his Mercedes in the backwoods in Oregon — and eating him alive?” She paused to see if this registered, examined
D.F. Bailey (Bone Maker (Will Finch Mystery, #1))
Look, there’s more to this than either of us thought.” Finch waited for her to continue. He knew the pattern: whenever she had new information, she needed to assess what part she could reveal to him. He realized she needed another prod. “Jennie, I didn’t have to tell you about the Whitelaw’s
D.F. Bailey (Bone Maker (Will Finch Mystery, #1))
One must demand of each and every one what he or she is capable of. Authority is first and foremost based on reason. If you order your people to throw themselves into the sea, you will have a revolution on your hands. I have the right to demand obedience because my orders are reasonable ones.
Antoine de Saint-Exupéry (The Little Prince)
Exactly. One must demand of each and every one what he or she is capable of. Authority is first and foremost based on reason. If you order your people to throw themselves into the sea, you will have a revolution on your hands. I have the right to demand obedience because my orders are reasonable ones.
Antoine de Saint-Exupéry (The Little Prince)
The differentiation of our sex organs takes place in the first months of pregnancy, while the sexual differentiation of the brain occurs in the second half of pregnancy. Since these two processes take place at different times, the theory is that in the case of transsexuality, they have been influenced independently of one another.
D.F. Swaab (We Are Our Brains: A Neurobiography of the Brain, from the Womb to Alzheimer's)
In 2004 Fox News reported that the widow married the man who’d been given her first husband’s heart. Her new husband went on to kill himself in the same way as the heart’s first “owner.” At the age of thirty-nine, Cheryl was widowed for the second time. De Telegraaf didn’t conclude from this that it might not have been easy to live with Cheryl.
D.F. Swaab (We Are Our Brains: A Neurobiography of the Brain, from the Womb to Alzheimer's)
When a pregnant woman experiences stress, the brain of a female fetus will become more male and vice versa. This also appears to be an adaptive response. A girl will be able to cope better in later life if she’s robust and competitive, while a boy who isn’t macho is less likely to get into conflict with alpha males in that stressful environment.
D.F. Swaab (We Are Our Brains: A Neurobiography of the Brain, from the Womb to Alzheimer's)
Our linguistic and cultural environments don’t determine only which brain systems are involved in language processing but also how facial expressions are interpreted and how we scan images and their surroundings. Japanese and New Guineans, for instance, find it difficult to distinguish between a face expressing fear and a face expressing surprise.
D.F. Swaab (We Are Our Brains: A Neurobiography of the Brain, from the Womb to Alzheimer's)
He pulled out stiff starched sheets, yellowed at the creases, each sheet embroidered with an elaborate medallion in which the letters D.F. twined above a garland of roses; some woman's trousseau from a hundred- two hundred- years back. There were other treasures too: sandalwood boxes of handkerchiefs, copper saucepans dulled with verdigris, an old radio from before the war, he guessed, its casing cracked to reveal tubes as big as doorknobs. Best of all was a huge old spice chest of rough black oak, some of its drawers still labeled in faded brown ink: Cannelle, Poivre Rouge, Lavande, Menthe Verte. The long-empty compartments were still fragrant with the scents of those spices, some dusted with a residue which colored his fingertips with cinnamon and ginger and paprika and turmeric.
Joanne Harris (Blackberry Wine)
It seems unlikely that premature babies can consciously feel pain before the twenty-ninth or thirtieth week. The pain sensors in the skin and the nerve pathways that convey pain signals are in place as early as the seventh week, enabling the fetus to respond to touch from a needle. But, contrary to the claims of fanatical pro-lifers, that certainly doesn’t constitute proof that the fetus can feel pain.
D.F. Swaab (We Are Our Brains: A Neurobiography of the Brain, from the Womb to Alzheimer's)
A hereditary defect in the DNA for ADH makes this hormone’s function immediately apparent. People who inherit this condition produce fifteen liters of urine a day. I have followed a family that has had the condition for five generations. It was during my internship in 1968 in Amsterdam’s Binnengasthuis Hospital that I first met them. At that time, the family’s life was largely dominated by urinating and drinking.
D.F. Swaab (We Are Our Brains: A Neurobiography of the Brain, from the Womb to Alzheimer's)
Su primera manifestación multitudinaria ocurrió en el Estadio Azteca, durante la inauguración del Mundial de 1986. El presidente Miguel de la Madrid tardó en aceptar ayuda internacional para no debilitar la ‘imagen de México’ y fue rebasado por las iniciativas ciudadanas. En el comienzo de el mundial recibió un abucheo sin precedentes. Fue el primer signo de que la mayoría de los habitantes del D.F. no iban a soportar más gobiernos del PRI.
Juan Villoro (8.8: El miedo en el espejo)
Relația mă transforma. Mă făcea să urăsc persoana pe care o vedeam în oglindă, căci era opusul a ceea ce voiam să fiu, dar îmi lipsea tăria să pun punct. Mă agățam de momentele în care lui îi păsase de mine, uitasem să închid ușa trecutului și prin ea vedeam lucruri a căror umbră nici măcar nu o mai zăream în prezent. Aparent, speranța e o lamă cu două tăișuri, pe care ești nevoit să o cuprinzi între degete, legat la ochi fiind. Iar eu preferam să strâng mai bine fașa în loc să încerc să privesc prin ea.
Silvia D.F. (Numele meu este Sonya (Pe urmele pașilor pierduți, #1))
Wynter's Pass was a picturesque region in the north of Vohlfhein, where the Bleak Hills eventually collapsed into the Frozen Sea. From the back of Mr. Buckles, who had been on a slow trot since sunrise, Monch watched the light glisten off of the frozen branches of the evergreens. As the sun warmed the frozen ground, sending the evening's frost into retreat, Monch absorbed the splendor of it all and wondered how expensive the local real estate must be around here. He then contemplated attempting to find an agent that would represent his interests well. "This land is such a spectacular wonder," the Lion of Ahriman declared. "It would be very much sought after if they could just do something about the bears, the White Orts, the wolves, the bloodthirsty cannibals, the snow manapés, the frost wizards, the northern bandit gangs, the dire lynxes, the similarly sounding but not related pygmy bloodthirsty cannibals, the demon possessed yaks, the dead-soul animated trees, the..." Monch paused for a moment. "It just occurred to me that this land is really not safe at all. It seems almost everything in it wants to kill me," the Templar admitted.
D.F. Monk (Tales of Yhore: The Chronicles of Monch)
of now, the main difference has been found in the HAR1 (human accelerated region 1), a segment of a recently discovered RNA gene. The RNA that is expressed in early development (HAR1F) is specific to the reelin-producing Cajal-Retzius cells in the brain. HAR1F comes to expression together with reelin in the seventeenth to nineteenth weeks of fetal development, a crucial stage in the formation of the six-layered cerebral cortex. The mutations in this human gene are probably over a million years old and could have played a crucial role in the emergence of modern humankind. Throughout our evolution, an enormous
D.F. Swaab (We Are Our Brains: A Neurobiography of the Brain, from the Womb to Alzheimer's)
Monch was on no simple retreat. The journey he had plotted for himself was much longer, and took him many buckets away from Appollon to Angarr's Sorrow, the land of fetid bogs in southeastern Sarthiss. This was a world far away from everything he knew... from everyone he knew. Granted, the list of people he knew was exceptionally short, especially since Monch was horrible with names and only slightly less horrible with faces. Regardless, he did not wish to accidentally advertise his inexperience to anyone he might possibly know, which is why he travelled so far afield. There were ruins in the swamps, ruins hidden under years of neglect and heavy with decay. Things lurked in those ruins, inhuman beasts with forbidden hungers. He intended to use the dangers of the swamps as the whetstone that would hone his abilities to a razor-keen edge. Monch would test his blade against and come back all the stronger... ...or dead. No... that wasn't right. Given the fact that he was immortal, death really wasn't an option. So then, he would come back stronger... ...or something something horrible. Monch decided to fill in those particular details later on, when he had time to ponder his autobiography at length. He would tidy up that particular idiom later.
D.F. Monk (Tales of Yhore: The Chronicles of Monch)
Since under the circumstances a person is no longer conscious of their own body, we of course shouldn’t interpret the reflex reactions of the spinal cord that occur when a surgeon removes organs from a brain-dead patient as an expression of pain. That’s easily said, but it’s quite a different thing for the surgeon who sees the body respond when he makes an incision to remove its organs. In the United Kingdom, anesthesia is administered for this procedure. The Dutch association of anesthetists finds this nonsensical, and scientifically speaking they’re right. In such cases an anesthetic is given to preserve not brain-dead patients but rather transplant surgeons from discomfort.
D.F. Swaab (We Are Our Brains: A Neurobiography of the Brain, from the Womb to Alzheimer's)
One of the most studied organisms in this context is the tiny polyp Hydra, which possesses only a hundred thousand cells. Its neural network is concentrated in its head and foot: a first evolutionary step toward developing a brain and spinal cord. Hydra’s nervous system contains a chemical messenger—a minuscule protein—that resembles two of our own: vasopressin and oxytocin. A protein of this kind is called a neuropeptide. In vertebrates, the gene for this particular neuropeptide first doubled and then mutated in two places, creating the two closely related but specialized neuropeptides vasopressin and oxytocin, which have recently become the focus of interest, partly because of their important role as messengers in our social brains (see chapter 9).
D.F. Swaab (We Are Our Brains: A Neurobiography of the Brain, from the Womb to Alzheimer's)
En Nueva grandeza mexicana (1946), uno de los ensayos más ingeniosos sobre la ciudad de México, Salvador Novo considera que toda ciudad moderna debe elegir uno de dos destinos posibles: o extinguirse y mantener intacta su arquitectura (como la ciudad maya de Chichen Itzá); o pertenecer viva, transformándose y renovándose constantemente. Las ciudades y sus habitantes, escribe Novo, “se enfrentan por inescapable determinismo a un incómodo dilema: o la cripta honorable o la vida imprevisible: o la momia o el hombre: o el museo o la urbe”. Hasta ahora la ciudad de México ha logrado mantenerse viva y evitar el destino de tantos otros centros urbanos menos afortunados, que se han convertido en museos al aire libre o en meras atracciones turísticas sin vida propia. “A diferencia de Teotihuacán” escribe Novo, “ha sido el destino de México sobrevivir a costa de transformarse
Rubén Gallo (México D.F.: Lecturas para paseantes)
gene, the mutation of whose DNA building blocks accelerated after the split between humans and chimpanzees, around 5.5 million years ago. The theory has also been put forward that the human brain is still evolving, on the grounds that a genetic variant of ASPM is thought to have originated only 5,800 years ago and then spread rapidly through the population. A genetic variant of the microcephalin gene (D allele of MCPH1), which regulates brain size, is thought to have only entered the DNA of Homo sapiens during the last ice age, around 37,000 years ago—yet 70 percent of the current world population carries this variant. A rapid increase of this kind is only possible if a variant confers a clear evolutionary advantage. Genes whose mutations are associated with human language have also been found. Mutations of the FOXP2 gene cause language and speech disorders that run in families. And ASPM and microcephalin also appear to have a linguistic connection.
D.F. Swaab (We Are Our Brains: A Neurobiography of the Brain, from the Womb to Alzheimer's)
As regards the DF 4000 Deluxe X-ray body scanner we were discussing, please be assured, I have never known a case of a husband “using it to track down shopping parcels hidden about his wife’s person.
Sophie Kinsella (Shopaholic to the Stars (Shopaholic, #7))
The test statistics of a t-test can be positive or negative, although this depends merely on which group has the larger mean; the sign of the test statistic has no substantive interpretation. Critical values (see Chapter 10) of the t-test are shown in Appendix C as (Student’s) t-distribution.4 For this test, the degrees of freedom are defined as n – 1, where n is the total number of observations for both groups. The table is easy to use. As mentioned below, most tests are two-tailed tests, and analysts find critical values in the columns for the .05 (5 percent) and .01 (1 percent) levels of significance. For example, the critical value at the 1 percent level of significance for a test based on 25 observations (df = 25 – 1 = 24) is 2.797 (and 1.11 at the 5 percent level of significance). Though the table also shows critical values at other levels of significance, these are seldom if ever used. The table shows that the critical value decreases as the number of observations increases, making it easier to reject the null hypothesis. The t-distribution shows one- and two-tailed tests. Two-tailed t-tests should be used when analysts do not have prior knowledge about which group has a larger mean; one-tailed t-tests are used when analysts do have such prior knowledge. This choice is dictated by the research situation, not by any statistical criterion. In practice, two-tailed tests are used most often, unless compelling a priori knowledge exists or it is known that one group cannot have a larger mean than the other. Two-tailed testing is more conservative than one-tailed testing because the critical values of two-tailed tests are larger, thus requiring larger t-test test statistics in order to reject the null hypothesis.5 Many statistical software packages provide only two-tailed testing. The above null hypothesis (men and women do not have different mean incomes in the population) requires a two-tailed test because we do not know, a priori, which gender has the larger income.6 Finally, note that the t-test distribution approximates the normal distribution for large samples: the critical values of 1.96 (5 percent significance) and 2.58 (1 percent significance), for large degrees of freedom (∞), are identical to those of the normal distribution. Getting Started Find examples of t-tests in the research literature. T-Test Assumptions Like other tests, the t-test has test assumptions that must be met to ensure test validity. Statistical testing always begins by determining whether test assumptions are met before examining the main research hypotheses. Although t-test assumptions are a bit involved, the popularity of the t-test rests partly on the robustness of t-test conclusions in the face of modest violations. This section provides an in-depth treatment of t-test assumptions, methods for testing the assumptions, and ways to address assumption violations. Of course, t-test statistics are calculated by the computer; thus, we focus on interpreting concepts (rather than their calculation). Key Point The t-test is fairly robust against assumption violations. Four t-test test assumptions must be met to ensure test validity: One variable is continuous, and the other variable is dichotomous. The two distributions have equal variances. The observations are independent. The two distributions are normally distributed. The first assumption, that one variable is continuous and the other dichotomous,
Evan M. Berman (Essential Statistics for Public Managers and Policy Analysts)
12.2. The transformed variable has equal variances across the two groups (Levene’s test, p = .119), and the t-test statistic is –1.308 (df = 85, p = .194). Thus, the differences in pollution between watersheds in the East and Midwest are not significant. (The negative sign of the t-test statistic, –1.308, merely reflects the order of the groups for calculating the difference: the testing variable has a larger value in the Midwest than in the East. Reversing the order of the groups results in a positive sign.) Table 12.2 Independent-Samples T-Test: Output For comparison, results for the untransformed variable are shown as well. The untransformed variable has unequal variances across the two groups (Levene’s test, p = .036), and the t-test statistic is –1.801 (df = 80.6, p =.075). Although this result also shows that differences are insignificant, the level of significance is higher; there are instances in which using nonnormal variables could lead to rejecting the null hypothesis. While our finding of insignificant differences is indeed robust, analysts cannot know this in advance. Thus, analysts will need to deal with nonnormality. Variable transformation is one approach to the problem of nonnormality, but transforming variables can be a time-intensive and somewhat artful activity. The search for alternatives has led many analysts to consider nonparametric methods. TWO T-TEST VARIATIONS Paired-Samples T-Test Analysts often use the paired t-test when applying before and after tests to assess student or client progress. Paired t-tests are used when analysts have a dependent rather than an independent sample (see the third t-test assumption, described earlier in this chapter). The paired-samples t-test tests the null hypothesis that the mean difference between the before and after test scores is zero. Consider the following data from Table 12.3. Table 12.3 Paired-Samples Data The mean “before” score is 3.39, and the mean “after” score is 3.87; the mean difference is 0.54. The paired t-test tests the null hypothesis by testing whether the mean of the difference variable (“difference”) is zero. The paired t-test test statistic is calculated as where D is the difference between before and after measurements, and sD is the standard deviation of these differences. Regarding t-test assumptions, the variables are continuous, and the issue of heterogeneity (unequal variances) is moot because this test involves only one variable, D; no Levene’s test statistics are produced. We do test the normality of D and find that it is normally distributed (Shapiro-Wilk = .925, p = .402). Thus, the assumptions are satisfied. We proceed with testing whether the difference between before and after scores is statistically significant. We find that the paired t-test yields a t-test statistic of 2.43, which is significant at the 5 percent level (df = 9, p = .038 < .05).17 Hence, we conclude that the increase between the before and after scores is significant at the 5 percent level.18 One-Sample T-Test Finally, the one-sample t-test tests whether the mean of a single variable is different from a prespecified value (norm). For example, suppose we want to know whether the mean of the before group in Table 12.3 is different from the value of, say, 3.5? Testing against a norm is akin to the purpose of the chi-square goodness-of-fit test described in Chapter 11, but here we are dealing with a continuous variable rather than a categorical one, and we are testing the mean rather than its distribution. The one-sample t-test assumes that the single variable is continuous and normally distributed. As with the paired t-test, the issue of heterogeneity is moot because there is only one variable. The Shapiro-Wilk test shows that the variable “before” is normal (.917, p = .336). The one-sample t-test statistic for testing against the test value of 3.5 is –0.515 (df = 9, p = .619 > .05). Hence, the mean of 3.39 is not significantly
Evan M. Berman (Essential Statistics for Public Managers and Policy Analysts)
different from 3.5. However, it is different from larger values, such as 4.0 (t = 2.89, df = 9, p = .019). Another example of this is provided in the Box 12.2. Finally, note that the one-sample t-test is identical to the paired-samples t-test for testing whether the mean D = 0. Indeed, the one-sample t-test for D = 0 produces the same results (t = 2.43, df = 9, p = .038). In Greater Depth … Box 12.2 Use of the T-Test in Performance Management: An Example Performance benchmarking is an increasingly popular tool in performance management. Public and nonprofit officials compare the performance of their agencies with performance benchmarks and draw lessons from the comparison. Let us say that a city government requires its fire and medical response unit to maintain an average response time of 360 seconds (6 minutes) to emergency requests. The city manager has suspected that the growth in population and demands for the services have slowed down the responses recently. He draws a sample of 10 response times in the most recent month: 230, 450, 378, 430, 270, 470, 390, 300, 470, and 530 seconds, for a sample mean of 392 seconds. He performs a one-sample t-test to compare the mean of this sample with the performance benchmark of 360 seconds. The null hypothesis of this test is that the sample mean is equal to 360 seconds, and the alternate hypothesis is that they are different. The result (t = 1.030, df = 9, p = .330) shows a failure to reject the null hypothesis at the 5 percent level, which means that we don’t have sufficient evidence to say that the average response time is different from the benchmark 360 seconds. We cannot say that current performance of 392 seconds is significantly different from the 360-second benchmark. Perhaps more data (samples) are needed to reach such a conclusion, or perhaps too much variability exists for such a conclusion to be reached. NONPARAMETRIC ALTERNATIVES TO T-TESTS The tests described in the preceding sections have nonparametric alternatives. The chief advantage of these tests is that they do not require continuous variables to be normally distributed. The chief disadvantage is that they are less likely to reject the null hypothesis. A further, minor disadvantage is that these tests do not provide descriptive information about variable means; separate analysis is required for that. Nonparametric alternatives to the independent-samples test are the Mann-Whitney and Wilcoxon tests. The Mann-Whitney and Wilcoxon tests are equivalent and are thus discussed jointly. Both are simplifications of the more general Kruskal-Wallis’ H test, discussed in Chapter 11.19 The Mann-Whitney and Wilcoxon tests assign ranks to the testing variable in the exact manner shown in Table 12.4. The sum of the ranks of each group is computed, shown in the table. Then a test is performed to determine the statistical significance of the difference between the sums, 22.5 and 32.5. Although the Mann-Whitney U and Wilcoxon W test statistics are calculated differently, they both have the same level of statistical significance: p = .295. Technically, this is not a test of different means but of different distributions; the lack of significance implies that groups 1 and 2 can be regarded as coming from the same population.20 Table 12.4 Rankings of
Evan M. Berman (Essential Statistics for Public Managers and Policy Analysts)
Frankenstein should be banned reading for scientists.’ ‘I’d be more inclined to make it compulsory reading for non-scientists
D.F. Jones (Colossus (Colossus Trilogy Book 1))
dicen que la crisis económica viene de fuera, es lo mismo que decir: “Perdonen a los criminales de casa que ellos no son culpables”. —
Guillermo Fadanelli (Hotel DF)
en el Distrito Federal? Sólo los héroes o los idiotas.
Guillermo Fadanelli (Hotel DF)
Son los políticos que quieren dejar huella y nada más acarrean destrozos.
Guillermo Fadanelli (Hotel DF)
En el Distrito Federal nadie extraña a nadie, todos desean la ausencia del otro, su desaparición repentina, se sueltan algunas lágrimas a causa de las pérdidas y después viene la felicidad.
Guillermo Fadanelli (Hotel DF)
luego. No podía ser un chino en general, tenía que ser un chino de Sinaloa, un local de Mexicali, o uno de la calle Dolores en el df. Voy a añadir eso la próxima vez que lo cuente —dijo Macario.
Paco Ignacio Taibo II (Sueños de frontera (Héctor Belascoarán Shayne, #7))
Zombie! Zombie! Brain Bang!
D.F. Noble (Zombie! Zombie! Brain Bang!)
Baby Armor D.F. Noble Narrated by Morgan Freeman
D.F. Noble (Zombie! Zombie! Brain Bang!)
after working in a restaurant for so long, he found himself hating people more and more.
D.F. Noble (Zombie! Zombie! Brain Bang!)
McDonald’s was being attacked by frenzied cannibals,
D.F. Noble (Zombie! Zombie! Brain Bang!)
(4151)GNP(4151) many other countries have requested the ACRC to provide them with technical assistance, and the UN and other international organizations have also paid attention to Korea as their partner for technical assistance in anti-corruption
kim89
El Von Humboldt barriobajero explorador, sabio y buscador de nuevas especies, ha creído encontrar un antro del tamaño de su melancolía.
Guillermo Fadanelli (Hotel DF)
Nietzsche said, Amor Fati. Love your fate.
D.F. Bailey (Second Life)
The thought of her mother’s expression made Valancy laugh – for she had a sense of humour nobody in her clan suspected.
L.M. Montgomery (The Blue Castle (DF Modern Classics Book 8))
Escribir sobre la ciudad de México es una empresa destinada al fracaso. Ignorante de esto, durante mucho tiempo pensé que para escribir sobre el DF debía imitar la tradición: convertirme, a lo Walter Benjamin, en una connaisseuse de las banquetas, botánica de la flora urbana, arqueóloga amateur de las fachadas del centro y los anuncios espectaculares del periférico. He intentado caminar como una petite Baudelaire por Copilco: imposible extraer una sola línea sobre Eje 10. ¿Será culpa de Copilco? Oí a alguien decir alguna vez que Copilco venía del náhuatl 'lugar de las copias'. Tras repetidas caminatas por aquella zona, puedo concluir sin temor a equivocarme que con eso queda dicho lo único que se puede decir sobre esa feísima porción de la ciudad, apéndice enfermizo de la Universidad Nacional Autónoma de México, donde se reproducen masivamente los libros de sus bibliotecas a diez centavos por página. Quizá sea culpa de Copilco.
Valeria Luiselli (Papeles falsos)
la noche del DF, una noche que a mí siempre me ha parecido preciosa, generalmente las noches aquí son frescas, brillantes, pero no frías, noches hechas para pasear o para coger, noches hechas para platicar sin apuro,
Roberto Bolaño (Los detectives salvajes)
enthusiasm for their subject to motivate them, to bring their subject alive and make learning an exciting, vivid and enjoyable experience.    It is teachers’ passion for their subject that provides the basis for effective teaching and learning. These teachers use their subject expertise to engage students in meaningful learning experiences that embrace content, process and social climate. They create for and with their children opportunities to explore and build important areas of knowledge, and develop powerful tools for learning, within a supportive, collaborative and challenging classroom environment. (DfES, 2003a: paras 1–
Vanessa Kind (Science: Teaching School Subjects 11-19)
Buscó en la libreta el número telefónico de Gilberto Suárez Torres, el procurador de Justicia del DF. Le pediría como un favor personal que ordenara a sus agentes madrear con tubo a ese gachupín abusivo. Suárez cultivaba su amistad y se desvivía por agasajarlo. No era para menos: tenía bien documentada su complicidad con los fayuqueros de Tepito, que le dejaba doscientos mil pesos al mes. No podía negarle un pequeño favor al periodista que mejor había encubierto su vasto repertorio de latrocinios
Enrique Serna (El vendedor de silencio)
Marilla, isn’t it nice to think that tomorrow is a new day with no mistakes in it yet?” “I’ll warrant you’ll make plenty in it,” said Marilla. “I never saw your beat for making mistakes, Anne.” “Yes, and well I know it,” admitted Anne mournfully. “But have you ever noticed one encouraging thing about me, Marilla? I never make the same mistake twice.” “I don’t know as that’s much benefit when you’re always making new ones.” “Oh, don’t you see, Marilla? There must be a limit to the mistakes one person can make, and when I get to the end of them, then I’ll be through with them. That’s a very comforting thought.
L.M. Montgomery (Anne of Green Gables : Complete 8 Books Set (DF Children's Classics Book 1))
Trist lucru să nu te cunoști măcar pe tine într-o lume plină de măști.
Silvia D.F. (Numele meu este Sonya (Pe urmele pașilor pierduți, #1))
Toți suntem buni și răi, deopotrivă. Depinde în povestea cui ne aflăm.
Silvia D.F. (În umbra timpului furat (Pe urmele pașilor pierduți, #2))