Pretend you want to determine whether the mean weekly sales

Pretend you want to determine whether the mean weekly sales of soup are the same when the soup is the featured item and when it is a normal item on the menu. When it is the featured item the sample mean is 66 and the population standard deviation is 3 with a sample size of 23. When it is a normal item the sample mean is 53 with a population standard deviation of 4 and a sample size of 7. Given this information we could use a t test for two independent means.

Solution

The situation is based on mean weekly sales of soup of two different population. To carry out the test of two independent means , sample mean sales of soup of two different samples are to be determined. Also, the population standard deviations of two population are known.

As, the two population standard deviations are known, so the sampling distribution of sample means follows normal distribution.

Finally, in this case t test can not used to test the two independent means. Here, two sample z test is appropriate.

Thus, the correct option is B.