The resting heart rates for 80 women aged 46−55 in a simple random sample are normally distributed, with a mean of 71 beats per minute and a standard deviation of 6 beats per minute. Assuming a 90% confidence level (90% confidence level=z-score of 1.645), what is the margin of error for the population mean? Remember, the margin of error, ME , can be determined using the formula ME is equal to the fraction with numerator z times s and denominator square root of n
Use the margin-of-error formula ME = z × s / √n. Substituting the values gives ME = 1.645 × 6 / √80 ≈ 9.87 / 8.94 ≈ 1.10 beats per minute, so the correct choice is 1.10.
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