We ask whether attending a private school leads to higher or lower performance on a test of social skills. A sample of 100 students from a private school produces a mean of 71.30 on the test, and the national mean for students from public schools is 75.62 (x = 28.0).

(a) Should we use a one-tailed or a two-tailed test? Why?

(b) What are H0 and Ha? (c) Compute zobt. (d) With = 0.05, what is zcrit? (e) What should we conclude about this relationship?

2. (a) In question 1 above, what is the probability that we made a Type I error? What would be the error in terms of the independent and dependent variables?

(b) What is the probability that we made a Type II error? What would be the error in terms of the independent and dependent variables?

3. Researcher A finds a significant relationship between increasing stress level and ability to concentrate. Researcher B replicates this study but finds a nonsignificant relationship. Identify the statistical error that each researcher may have made.