Question 3

Two high school chemistry teachers Ms Chan and Mr Lee are interested in knowing whether there is any variation in the way they grade the exams. They each grade the same set of 41 exams. Ms Chan's grades have a variance of 55.3 while Mr Lee's grades have a variance of 86.9. At the 1% level of significance, is there sufficient evidence to say

that Ms Chan's exam grade variance is smaller than Mr Lee? What assumptions must be made? (Use the critical value approach.)

Question 4

A random sample of 17 sales associate in Pucci Boutiques has an average monthly income of $35,800 and a standard deviation of $7,800. In Brada Boutiques, a random sample of 18 sales associate has an average monthly income of $35,100 and a standard deviation of $7,375. At 1% level of significance, is there enough evidence to reveal that the mean monthly incomes in the two boutiques are different? List out the assumption(s). (Use the critical value approach method.)