Question: A clinical trial is planned to compare an experimental mediation designed to lower blood pressure to a placebo. Before starting the trial, a pilot study is conducted involving 10 participants. The objective of the study is to asses how systolic blood pressure changes untreated over time. Systolic blood pressures are measured at baseline and again 4 weeks later. Compute a 95% confidence interval for the mean difference in blood pressures over 4 weeks.

Baseline: 120, 145, 130, 160, 152, 143, 126, 121, 115, 135

Four weeks: 122, 142, 135, 158, 155, 140, 130, 120, 124, 130