Grape juice and blood pressure Researchers who wanted to see if drinking grape juice could help people lower their blood pressure got 120 non-smokers to volunteer for a study.
They measured each person's blood pressure and then randomly divided the subjects into two groups. One group drank a glass of grape juice every day while the other did not. After sixty days the researchers measured everyone's blood pressure again. They reported that differences in changes in blood pressure between the groups were not statistically significant.
a. Was this an experiment or an observational study? Explain briefly.
b. Briefly explain what not statistically significant means in this context.
c. Briefly explain why the researchers randomly assigned the subjects to the groups.
d. Since everyone's blood pressure was measured at the beginning and at the end of the study, the researchers could have simply looked at the grape juice drinkers to see if their blood pressure changed. Briefly explain why the researchers bothered to include the control group.
e. Briefly explain why the researchers studied only non-smokers.
f. Other researchers now plan to replicate this study using both smokers and non-smokers. Briefly describe the design strategy you think they should use.
Question 2
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