The mean gross annual incomes of certified tack welders are normally distributed with the mean of $50,000 and a standard deviation of $4,000. The ship building association wishes to find out whether their tack welders earn more or less than $50,000 annually. The alternate hypothesis is that the mean is not $50,000. If the level of significance is 0.10, what is the decision rule?
A) Do not reject the null hypothesis if computed z lies between -1.65 and +1.65; otherwise, reject it.
B) Do not reject the null hypothesis if computed z is greater than 1.65; otherwise, reject it.
C) Do not reject the null hypothesis if computed z lies between -1.96 and +1.96; otherwise, reject it.
D) Reject the null hypothesis if computed z is below -1.96; otherwise, reject it.

Question

Quizplus · Accepted Answer

Since the alternate hypothesis suggests the mean could be either more or less than $50,000 (a two-tailed test), and the level of significance is 0.10, the critical z-values for a two-tailed test at this significance level are -1.65 and +1.65.

The Mean Gross Annual Incomes of Certified Tack Welders Are