Given:
Confidence level = 90%
mean = 71 beats per minute
standard deviation = 6 beats per minute
margin of error = z δ / √n
where : δ - population of the standard deviation, n is the sample size ; z is the appropriate z value.
90% confidence level = 1.645 in z-value
margin of error = 1.645 (6/√80) = 1.645 (6/8.94) = 1.645 0.671 = 1.104
The margin of error is 1.10
