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, 67) distribution.
Minutes of activity for lean people had the N(526, 107) distribution.
Within what limits do the active minutes for 95% of the people in each group fall?
Use the 68–95–99.7 rule.

Within what limits do the active minutes for 95% of the people in the mildly obese group fall?
A. Within 306 to 440 minutes.
B. Within 134 to 612 minutes.
C. Less than 239 or more than 507 minutes.
D. Within 239 to 507 minutes.

Please help, thank you! I don't know how to set it up or where to even begin.

3 answers

Z = (score-mean)/SD

95% = Z = ±1.96

Values for A-D are not 95%.

Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the percentages related to the Z scores.
D. Within 239 to 507 minutes.
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 is normally distributed with mean 373 minutes and standard deviation of 67 minutes. The least active 20% of these individuals spend at most 317 minutes walking or standing because 317 = _____*67 + 373. Enter your answer rounded to two decimal places.