There is a certain compound found in the cacao plant that can affect blood pressure. A researcher is studying whether adding a capsule that contains this compound along with regular medication will aid in reducing blood pressure. The researcher recruited 22 volunteer patients who had approximately the same blood pressure and were taking the same brand of blood pressure medicine. The researcher randomly assigned 11 of the volunteers to take the compound capsule along with their current medication and the other 11 of the volunteers to take a placebo capsule along with their current medication. After one month, the systolic blood pressure, in millimeters of mercury (mmHg), was taken for the volunteers and recorded. The table displays summary statistics for the systolic blood pressure for each group of volunteers.(含图)
Assuming all conditions for inference are met, which of the following is a 95 percent confidence interval for the difference between the means of the systolic blood pressure (compound minus placebo), in mmHg, for all patients similar to those in the study?