1. A professor posed a hypothesis that there was no significant difference between boys and girls on their soda consumption per day in an elementary school. He randomly sampled 25 boys and 25 girls. The mean soda consumption for boys was 40 oz per day and the standard deviation was 5. The mean soda consumption for girls was 30 oz per day and the standard deviation was 5. What is the standard error of the difference in means? (show work)
2. We can use pairwise comparison if we want to compare the means between the average GPA in 8 different schools.
a. Yes
b. No
3. A professor wants to test all possible pairwise comparisons among all four means. If we need to maintain an "experiment-wise" alpha of 0.01, what is the error rate per comparison after applying Bonferroni correction? (show work)
4. The value of t will increase as the standard deviation of difference___ and the difference between means___.
a. Increases; decreases
b. Increases; Increases
c. Decreases; decreases
d. Decreases; Increases
5. 1-β is the probability of_______
a. Rejecting a true null hypothesis
b. Accepting a true null hypothesis
c. Accepting a false null hypothesis
d. Rejecting a false null hypothesis
6. If the probability that you will correctly reject a false null hypothesis is 0.80 at 0.10 significance level, α is__ and power is__.
a. 0.10, 0.20
b. 0.10, 0.80
c. 0.90, 0.20
d. 0.99, 0.80
7. If the significance level changes from 0.05 to 0.01, the power will___
a. Increase
b. Decrease
c. Stay the same
d. First increase, then decrease
8. Which of the following descriptions are correct?
a. Increasing sample size from 5 to 25 will increase power to a greater degree than increasing sample size from 15 to 35.
b. Increasing sample size from 60 to 80 will increase power to the same degree as increasing sample size from 200 to 220.
c. Increasing sample size from 40 to 60 will decrease power to a greater degree than increasing sample size from 60 to 80.
d. Increasing sample size from 50 to 70 will decrease power to the same degree as increasing sample size from 70 to 90.
9. Which of the following descriptions are correct regarding power (select all that apply)?
a. Changing from a one-tailed test to a two-tailed test can increase power
b. Increasing sample size can increase power
c. Increasing standard deviation will decrease power
d. Changing from a one-tailed test to a two-tailed test, or changing from a two-tailed test to a one-tailed test will not change power
10. Which of the following are correct (select all that apply)?
a. Researchers need to be aware that there is a tradeoff between significance level and power
b. Researchers can increase power of experiments by increasing sample size
c. Researchers can increase power of experiments by increasing significance level
d. Researchers need to know that the larger the effect size, the more likely that an experiment would find a significant effect