Question

n a study of 250 adults, the mean heart rate was 70 beats per minute. Assume the population of heart rates is known to be approximately normal with a standard deviation of 12 beats per minute. What is the 99% confidence interval for the mean beats per minute?

Answer 1

We are given mean = 70, SD = 12, sample size n = 250, and for a 99% confidence interval, the two-tailed z-score is +/-2.58.
The CI bounds are calculated as:
mean +/- z*SD/sqrt(n) = 70 +/- 2.58*12/sqrt(250) = 68.04 to 71.96 beats per minute