In a study of 225 adults, the mean heart rate was 72 beats per minute. Assume the population of heart rates is known to be approximately normal with a standard deviation of 10 beats per minute. What is the 90% confidence interval for the mean beats per minute?

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Mathematics

Naomi Friedman

24 December, 17:02

In a study of 225 adults, the mean heart rate was 72 beats per minute. Assume the population of heart rates is known to be approximately normal with a standard deviation of 10 beats per minute. What is the 90% confidence interval for the mean beats per minute?

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Atkinson · Answer 1

90% CI z * = 1.64

x bar = 72

n = 225

s = 10

x + - z * (s/sqrt n)

72 + - 1.64 (10/sqrt225)

72 + - 1.64 (10/15)

72 + - 1.64 (2/3)

72 + 1.64 (2/3) = 73.09

72 - 1.64 (2/3) = 70.91