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# What should be the null hypothesis?

1. A 'rare' outcome, due to an extreme value found for the sample mean relative to the population mean, signifies that the null hypothesis should be:
a. retained
b. rejected
c. accepted
d. none of the above

Question 2
1. To express a sample mean as a Z value:
a. subtract the hypothesized population mean.
b. subtract the hypothesized population mean and divide by the standard deviation.
c. subtract the hypothesized population mean and divide by the standard error of the mean.
d. subtract the hypothesized population mean and divide by the variance.

Question 3
1. Given critical z values of ±1.96 and an observed z value of -2.40, the appropriate decision is to:
a. neither retain nor reject, but conduct another investigation
b. neither retain nor reject, but increase the size of the sample
c. reject the null hypothesis
d. retain the null hypothesis

Question 4
1. Given an observed difference between a sample mean of 42 and a hypothesized population mean of 50, you:
a. can conclude that the null hypothesis is true
b. must determine whether this observed difference can reasonably be attributed to chance
c. can retain, but not accept, the null hypothesis
d. can conclude that the alternative hypothesis is true

Question 5
1. A decision to reject the null hypothesis implies that:
a. there is a lack of support for the alternative hypothesis
b. there is support for the alternative hypothesis
c. the sample is probably not representative
d. the sample size is probably too small
e. none of the above

Question 6
1. Compared to a two-tailed hypothesis test, a one-tailed test is more likely to detect a:
a. true null hypothesis
b. false null hypothesis in the direction of concern
c. false null hypothesis
d. true null hypothesis in the direction of concern

Question 7
1. When the rejection of a true null hypothesis would have unusually disastrous consequences, it is best to set your level of significance equal to:
a. .10
b. .05
c. .01
d. .001

Question 8
1. If your observed sample mean were exactly equal to your population mean (assuming some moderate variation in both the sample and the population), then your z value would be:
1. 1.96
2. 1.65
3. 2.58
4. 0
5. not enough information to determine

Question 9
1. In an experiment to determine whether TV cartoons produce more aggressive behavior in grade school children, the null hypothesis would state that TV cartoons have:
a. an effect on aggressive behavior
b. only a slight effect on aggressive behavior
c. no effect on aggressive behavior
d. a statistically significant effect on aggressive behavior

Question 10
1. If the null hypothesis is in reality false, and the z value of the randomly selected sample doesn't deviate beyond the critical z value, the null hypothesis will be:
1. correctly retained
2. correctly rejected
3. incorrectly retained
4. incorrectly rejected

Question 11
1. Two ways to increase the likelihood of detecting a real effect are to _______ sample size and to _______ alpha.
a. increase; decrease
b. increase; increase
c. decrease; decrease
d. decrease; increase

Question 12
1. You're testing a new vitamin pill that could save many lives if it works even a little bit, and would do no harm even if it did not have any real effect. Given that there is often a trade off between risking Type I and Type II error, which type should you concentrate on minimizing in this situation?