A cheese manufacturer is seeking to determine whether two different kinds of packaging of a certain kind of cheese differ in their ability to protect cheese from mold ? To do so, 80 equal-sized pieces of cheese are cut from one randomly selected block, 40 are packaged by Method A and 40 are packaged by Method B and at 40 different locations, one Method A pack and one Method B pack are left until mold appears ? The results (in days) before mold appears are provided in below data sheet "Cheese_data.xlsx"

a. Form a 95% confidence interval for the difference between population mean time until mold appears for the two methods and interpret the confidence interval

b. Set the null and alternative hypotheses to test whether there is a difference between the abilities of the two different kinds of packaging to protect the cheese from mold

"Cheese_data.xlsx" ?