A family owned candy company recently hired many new staff members to deal with an increase in demand. They have a day shift (Team A) and a night...

A family owned candy company recently hired many new staff members to deal with an increase in demand. They have a day shift (Team A) and a night shift (Team B). Although they are quite happy with their new employees they suspect that some of them may be eating chocolates when they are not looking.

Their signature box weighs 1.87 kgs.

They randomly sampled 9 boxes from Team B and found that on average they weighed 1.37 kgs.

Using the data they collected, the family would like to test whether μ

μ, the mean weight of chocolate per box, is less than their original signature box.

Suppose that the weight of chocolate per box is normally distributed with a standard deviation σ=.75kg

σ=.75kg.

Which of the following is the correct test-statistic in this case?

 z = .67

z = -2

z = -4

z = 1.33

z = 2

z = 4

z = -.67

z = -1.33