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 difference_{}is (7.327, 18.67). This means that we can claim that_{}at the 0.05 significance level.

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