Researchers designed a study looking at cardiovascular deaths comparing a new drug to placebo. They determined that they would need 200 patients in the group to detect a 15% difference in cardiovascular end points given 90% power and significance level of 0.01. Which of the following would require researcher to increase the sample size?

a. Aim to detect a difference of 20%.

b. Specify power of 95%.

c. Use a significance level of 0.05.

d. Specify power of 80%.