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? do not reject the null hypothesis if computed z lies between -1.96 and 1.96; otherwise, reject it do not reject the null hypothesis if computed z lies between -1.65 and 1.65; otherwise, reject it do not reject the null hypothesis if computed z is greater than 1.65; otherwise, reject it reject the null hypothesis if computed z is below -1.96; otherwise, reject it