Brand x and brand y of pain relievers were tested to see how much ibuprofen each table contained. Does brand x have more ibuprofen? Test at the .05 level.

Solution: We are testing the hypotheses:

We need to use a two-tailed t-test to test the null hypothesis. We use Statdisk to compute the value of the t-statistics (since the sample size is big enough we are going to use a normal approximation):

The test statistics is equal to 4.4914, and the critical values are. This means that we reject the null hypothesis. We also observe that the 95% confidence interval for the differenceis (7.327, 18.67). This means that we can claim thatat the 0.05 significance level.