When engaging in weight-control (fitness/fat burning) types of exercise, a perso

Question

When engaging in weight-control (fitness/fat burning) types of exercise, a person is expected to attain about 160% of their maximum heart rate. For 20-year-olds, this rate is approximately 120 bpm. A simple random sample of one hundred 20-year-olds was taken, and the sample mean was found to be 107 bpm with a standard deviation of 45 bpm. Researchers wonder if this is evidence to conclude that the expected level is actually lower than 120 bpm.

A 95% Confidence Interval will have a Margin of Error of ____.
( round to the hundredths place)

Explanation / Answer

Solution:

From the given information
Sample mean x = 107,
Standard deviation s = 45
sample size n = 100

confidence interval :

z(0.975)=1.96

Margin of error = Z/2 * (s/n) = 1.96 * (45/sqrt(100)) = 8.82
C.I = x ± ME
= 107 ± 8.82
= (98.18, 115.82)

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