The document discusses an experiment to test the effectiveness of a blood pressure drug by measuring systolic pressure in a sample of people before and after taking the drug. The experimenter aims to show that the average reduction in systolic pressure is 20 or more. He will take measurements before and after administering the drug, then test if the difference between the mean pressures is greater than 20 at a certain statistical significance level. If the null hypothesis is not rejected, he can claim the reduction is 20 or more at that level of significance.