Design of CD case

X   ~   binomial (n = 90, π)

H0:   π = 1/3        HA:   π > 1/3


The more expensive of the 3 cases was chosen 36 times.

This is another example where the binomial distribution is used to find the p-value for testing a proportion.

Drag the slider to find the binomial probability of the expensive case being chosen 36 or more times.

p-value = 0.11 so there is no evidence of preference for the expensive case.

Use the slider and discuss how different numbers choosing the expensive case would change the conclusion.

The context is a trial of three CD cases in which all three were offered for sale at the same price in a CD store. Out of the first 90 cases that were purchased, 36 were the design that was more expensive to manufacture than the other two. Since more than a third chose this case design, is there strong evidence that customers prefer it?