Question

There was a lawsuit against Starbucks claiming that their lattes are being under filled. We know that a grande size cup should be 16 oz. The Today Show decided to do a test to see if they actually are being under filled. They went out and got 6 lattes and found that the average amount of liquid in each was 13.22 oz, with a sample standard deviation of 2.05. We are interested in determining if there is evidence that the lattes are being under filled. Use alpha= 0.01. Find the 99% confidence interval for the number of oz the lattes are being filled with.

The test statistic is:

The p-value is:

What conclusion would be made here?

Answer 1

Null and alternative hypothesis:

Test statistic:

df = 6-1= 5

p-value = T.DIST(-3.322, 5, 1) = 0.0105

Conclusion:

As p-value = 0.0105 > 0.01, we fail to reject the null hypothesis.

There is not enough evidence to claim that the lattes are being under filled, at the 0.01 significance level.

Confidence interval:

At = 0.01, critical value, = T.INV.2T(0.01, 5) = 4.032

99% confidence interval: