Question

It takes the average adult 22 minutes to walk a mile, with a standard deviation of 6 minutes. About what percentage of adults take longer than 27 minutes to walk a mile? Note: Assume that a Normal model is appropriate for the distribution of walking times. 29.67% 70.33% 20.33% 79.67%

Answer 1

The correct answer is C. 20.33%

Explanation:

1. Let's review all the information given to us to answer the question correctly.

Mean of time of adults walking a mile = 22 minutes

Standard deviation = 6 minutes

Normal distribution for the walking times

2. What percentage of adults take longer than 27 minutes to walk a mile?

27 minutes = Mean + 5 minutes

27 minutes = Mean + 0.83 * Standard deviation

Using the z table for z = 0.83, we have that:

P (z) = 0.7967

Therefore the probability of adults that take longer than 27 minutes walking a mile is:

1 - 0.7967 = 0.2033

The correct answer is C. 20.33%