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

Multiple Choice

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 critical value?

A) 1.65
B) 2.58
C) 1.28
D) $\pm$ 1.28
E) $\pm$ 1.645