*3. Suppose that the personnel director in Problem 1 wants to know whether the keyboarding speed of secretaries at her company is different from the national mean of 50.

(a) State H0.

(b) Which form of H1 is appropriate in this instance—directional or nondirectional?

(Explain.)

(c) State H1.

(d) Specify the critical values, z.05 and z.01.

statistical hypothesis testing significance testing indirect proof null hypothesis nondirectional alternative hypothesis directional alternative hypothesis test statistic z ratio one-sample z test one- versus two-tailed test exact probability (p value)

level of significance alpha region(s) of rejection critical region(s)

critical value(s)

region of retention decision error Type I error Type II error statistically significant statistically nonsignificant statistical significance versus importance Exercises 237