For each sample, do a test for zero correlation. (a) Use Appendix D to find the critical value of tα. (b) State the hypotheses about. (c) Perform the t test and report your decision.
a. r = + .45, n = 20, α = .05, two-tailed test
b. r = – .35, n = 30, α = .10, two-tailed test
c. r = + .60, n = 7, α = .05, right-tailed test
d. r = – .30, n = 61, α = .01, left-tailed test