Answer: 1.645
Step-by-step explanation:
Given : The mean annual income of certified welders is normally distributed with a mean of $50,000 and a population standard deviation of $2,000.
Alternative hypothesis :

Since the alternative hypothesis is two-tailed , so the hypothesis test is a two-tailed test.
Also, Significance level :

For two tailed test the to find the critical value , we need to find the z value or t-value for significance level of
.
The critical value will be:
