13. State the total degrees of freedom for the following t tests:

n = 12 for a one-sample t test

Critical value = 1.645 for a one-tailed test, = .05

df1 = 12, n2 = 19 for a two-independent-sample t test

Critical value = 63.657 for a two-tailed test, = .01

15. State the critical values for a two-independent-sample t test given the following conditions:

Two-tailed test, = .01, total df = 26

One-tailed test, lower-tail critical, = .01, df = 15 for each group

Two-tailed test, = .05, n = 12 in each group

One-tailed test, upper-tail critical, = .05, n for both groups combined is 30

17. A researcher reports the following confidence interval for a comparison of the difference between two groups: 95% CI 12.0 [30.0 to 6.0]. If there was no difference between groups, then a difference of 0 was expected.

What would the decision have likely been if the researcher tested this hypothesis with hypothesis testing at a .05 level of significance? Explain.

What is the value of the point estimate?

19. While researching lifestyle changes to improve happiness, you come across a research article reporting that pet owners self-reported greater overall happiness compared to those who do not own a pet, t(50) = 2.993, p < .05. Based on the information provided, answer the following questions:

Does the test statistic show a significant effect? Explain.

Would the confidence interval for this effect envelop 0? Explain.