Independent samples of 400 observations are selected from two populations.
Sample 1 Sample 2
mean= 5275 mean= 5240
standard deviation= 150 standard deviation= 200
a) Use a 90% confidence interval to estimate (µ1-µ2)
b) Test the null hypothesis µ1-µ2= 25 against the alternative hypothesis µ1-µ2≠ 25 at the significance level a= .05