Researchers are interested in evaluating the effect of a natural product on reducing blood pressure.

This will be done by comparing the mean reduction in blood pressure of a treatment (natural product) group and a placebo group using a two-sample t test. The researchers would like to be able to detect whether the natural product reduces blood pressure by at least 7 points more, on average, than the placebo. If groups of size 50 are used in the experiment, a two-sample t test using a = 0.01 will have a power of 80% to detect a 7-point difference in mean blood pressure reduction.

If the researchers want to be able to detect a 5-point difference instead, then the power of the test

(a) would be less than 80%.

(b) would be greater than 80%.

(c) would still be 80%.

(d) could be either less than or greater than 80%, depending on whether the natural product is effective.

(e) would vary depending on the standard deviation of the data.