Question

Suppose an investigator is interested in comparing the weight (ounces) of components produced by two different machines. They are interested in being able to detect a difference of 0.25 ounces between average weights of the components produced by the two different machines, and they believe the variance of the weights will be equal for the two machines being studied. They are conducting a two-sided test with a significance level of a = 0.05. Using preliminary data they have estimated the common standard deviation of the weight to be 0.4 ounces. What is the total number of samples they would need to achieve a power of 0.9?

Using minitab.

Answer 1

Minitab:

Stat-->Power and sample size-->2 sample t

Ans : 55+55 = 110.