The Mean Gross Annual Incomes of Certified Welders Are Normally $\pm$

Multiple Choice

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 critical value?

A) 1.65
B) 1.28
C) $\pm$ 1.28
D) $\pm$ 1.65