##### Stats final

What is the difference between the denominator of the equation for
the *z* score and that of the *z *statistic?

**C)**

**When computing a z score, we divide by the population
standard deviation, but when computing a z statistic, we
divide by the standard error of the sampling distribution.**

Under what conditions is it permissible to proceed with a hypothesis test even though the assumption that participants are randomly selected is violated?

**A**)

**We are cautious about generalizing the results.**

________ requires that all members of a population have an equal chance of being selected for a study.

**A)**

**Random selection**

Because of the principle of ________, when sample sizes are at least 30, the distribution will most likely resemble a normal distribution.

**C)**

**central limit theorem**

The null hypothesis states that:

**D)**

**there are no differences between the populations being studied.**

A *New York Times* article published on April 24, 2007,
reported the research of Dr. Giorgio Vallortigara, a neuroscientist at
the University of Trieste, Italy, and his two colleagues. The
researchers asked whether a dog wags its tail in a preferred direction
in response to positive stimuli and in another direction in response
to negative stimuli. To answer their question, they recruited 30 dogs
that were family pets. Filming each dog from above, they allowed it to
view (through a slat in its cage) three positive stimuli separately,
in order of descending positivity: its owner, an unfamiliar human, and
a cat. All the dogs responded by wagging their tails to the right. But
when the dogs were presented with an unfamiliar, aggressive dog, a
negative stimulus, all dogs wagged their tails to the left.

Which of the following statements is the null hypothesis for this study?

**B)**

**A dog's tail wagging will be the same in response to positive
stimuli as to negative stimuli.**

The typical probability adopted by researchers to determine whether a result is statistically significant is:

.01.

**B)**

**.05.**

Mehl (2007) published a study in the journal *Science*
reporting the results of an extensive study of 396 men and women
comparing the number of words uttered per day by each sex. If Mehl was
testing the idea that women talk more than men do, the null hypothesis
for the study would be ________ and the research hypothesis would be
________ (in symbolic terms).

**B)**

Ho:M1<M2;1;M1>M2

If a researcher is testing the idea that women talk more than men do, he/she could use a ______ test, whereas if a researcher is testing the statement “It is hypothesized that men and women will differ on the number of words uttered per day, ” he/she must use a _____ test:

**B)**

**one-tailed; **
**two-tailed**

When hypothesis testing, a conservative approach is to use a ________ rather than a ________.

**A)**

**two-tailed test; one-tailed test**