STAT Exam 2

A distribution of all sample means or sample variances that could be obtained in samples of a given size from the same population are called A. a conditional procedure B. a sampling distribution C. sampling without replacement D. random sampling

B

A method for testing a claim or hypothesis about a parameter in a population, using data measured in a sample, is called

Hypothesis Testing

9. Based on the effect size conventions, d = 0.60 is a small effect size medium effect size large effect size No answer text provided.

medium effect size

2. A researcher believes that increasing attention given to children will improve mean academic performance. Therefore, the alternative hypothesis should be: A. Mean academic performance will increase B. Mean academic performance will decrease C. Mean academic performance will not change D. Mean attention will increase

A. Mean academic performance will increase

4. What is the typical level of significance for a hypothesis test in behavioral research? .05 .01 .001 .50

.05

7. A researcher obtains z = 1.45 for a one-sample z test. What is the decision for this test at a .05 level of significance? to reject the null hypothesis to retain the null hypothesis It depends on whether the test is one-tailed or two-tailed. There is not enough information to make a decision.

to retain the null hypothesis

A distribution of Z scores are distributed in what type of unit measurement? A. binomial outcomes B. probabilities C. Standard deviation Units D. depends on the shape of the distribution

C.

A normal distribution has all of the following characteristics except that A. It is symetrical B. its distribution is theoretical C. the total area under the curve is greater than 1.0 D. The mean, median, and mode are equal

C.

State whether the first area is bigger, the second area is bigger, or the two areas are equal: the area to the left of z=.80, or the area to the right of z= -.80 A. The first is bigger B. The second is bigger C. The two areas are the same

C.

3. A professor gives an exam in which the mean score is 78 points. She gives another exam to test whether or not scores change. In this example, the null hypothesis is A. μ does not equal 78 B. xbar does not equal 78 C. μ = 78 D. xbar = 78

C. μ = 78

The alpha level indicates A. the probability of committing a type I error B. the probability of incorrectly rejecting the null hypothesis C. the probability of value for the rejection region D. All of the above

D.

What is the central limit theorem? A. it explains that sample means will vary minimally from the population mean. B. It explains that a sampling distribution of possible sample means is approximately normally distributed, regardless of the shape of the distribution in the population C. It explains that if we select a random sample, then on average we can expect the sample mean to equal the population mean D. All of the Above

D.

10. A researcher conducts a hypothesis test to evaluate the effect of a treatment. The hypothesis test produces a z-score of z=2.37. Assuming that the researcher is using a two-tailed test, what decision should be made? The researcher should reject the null hypothesis with a=.05, but not with a=.01 The researcher should reject the null hypothesis with either a=.05 or a=.01 The researcher should fail to reject the null hypothesis with either a=.05 or a=.01 Cannot answer without additional information

The researcher should reject the null hypothesis with a=.05, but not with a=.01

What happens to the standard error of the mean as sample size increases?

It decreases

6. Researchers state a level of significance in terms of an alpha level. The alpha level indicates the probability of committing a Type I error the probability of incorrectly rejecting the null hypothesis the probability value for the rejection region all of the above

all of the above

8. ________ allows researchers to describe (1) how far mean scores have shifted in the population, or (2) the percentage of variance that can be explained by a given variable. significance probability power effect size

effect size