Question

It appears that people who are mildly obese are less active than leaner people. One study looked at the average number of minutes per day that people spend standing or walking. Among mildly obese people, minutes of activity varied according to the N(373, 61) distribution. Minutes of activity for lean people had the N(525, 104) distribution. Within what limits do the active minutes for 95% of the people in each group fall

Answer 1

Among mildly obese people, 95% of the people have between 251 and 495 minutes of activity per day.

Among lean people, 95% of the people have between 317 and 733 minutes of activity per day.

Explanation:

The Empirical Rule states that, for a normally distributed random variable:

68% of the measures are within 1 standard deviation of the mean.

95% of the measures are within 2 standard deviation of the mean.

99.7% of the measures are within 3 standard deviations of the mean.

Within what limits do the active minutes for 95% of the people in each group fall

By the Empirical Rule, within 2 standard deviations of the mean.

Mildly obese:

Mean = 373, standard deviation = 61.

373 - 2*61 = 251 minutes

373 + 2*61 = 495 minutes

Among mildly obese people, 95% of the people have between 251 and 495 minutes of activity per day.

Lean people:

Mean = 525, standard deviation = 104

525 - 2*104 = 317 minutes

525 + 2*104 = 733 minutes

Among lean people, 95% of the people have between 317 and 733 minutes of activity per day.