The Mean Gross Annual Incomes of Certified Tack Welders Are

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) ±1.28
E) ±1.645