The mean gross annual incomes of certified welders are normally distributed with the mean of $20,000 and a standard deviation of $2,000. The ship building association wishes to find out whether their welders earn more or less than $20,000 annually. The alternate hypothesis is that the mean is not $20,000. 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

The level of significance is 0.10, so the critical values are -1.65 and +1.65. The decision rule is to not reject the null hypothesis if the computed z lies between -1.65 and +1.65, and to reject it otherwise.

The Mean Gross Annual Incomes of Certified Welders Are Normally