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, the mean number of minutes of daily activity (standing or walking) is approximately Normally distributed with mean 371 minutes and standard deviation 65 minutes. The mean number of minutes of daily activity for lean people is approximately Normally distributed with mean 528 minutes and standard deviation 108 minutes. A researcher records the minutes of activity for an SRS of 6 mildly obese people and an SRS of 6 lean people.Use z-scores rounded to two decimal places to answer the following:What is the probability (Image for It appears that people who are mildly obese are less active than leaner people. One study looked at the averag0.0001) that the mean number of minutes of daily activity of the 6 mildly obese people exceeds 420 minutes? What is the probability (Image for It appears that people who are mildly obese are less active than leaner people. One study looked at the averag0.0001) that the mean number of minutes of daily activity of the 6 lean people exceeds 420 minutes?

Answer 1

Answer:

0.0322; 0.9929

Step-by-step explanation:

Since the data is normally distributed, we use z scores for these probabilities.

The formula for a z score of a sample mean is

$z=\frac{\bar{X}-\mu}{\sigma \div \sqrt{n}}$

For the sample of mildly obese people, the mean, μ, is 371; the standard deviation, σ, is 65; and the sample size, n, is 6.

Using 420 for X,

z = (420-371)/(65÷√6) = 49/(65÷2.4495) = 49/26.5360 ≈ 1.85

Using a z table, we see that the area under the curve to the left of this is 0.9678.  However, we want the area to the right, so we subtract from 1:

1-0.9678 = 0.0322

For the sample of lean people, the mean, μ, is 528; the standard deviation, σ, is 108; the sample size, n, is 6.

Using 420 for X, we have

z = (420-528)/(108÷√6) = -108/(108÷2.4495) = -108/44.0906 ≈ -2.45

Using a z table, we see that the area under the curve to the left of this is 0.0071.  We want the area under the curve to the right, so we subtract from 1:

1-0.0071 = 0.9929