Chapter 6, Problem 16P

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8th Edition

Frederick J Gravetter + 1 other

ISBN: 9781133956570

Textbook Problem

According to a recent, people smile an average of μ = 62 time per day. Assuming that the distribution of smiles is approximately normal with a standard deviation of σ = 18, find each of the following values.

- a. What proportion of people smile more than 80 times a day?
- b. What proportion of people smile at least 50 times a day?

**(a)**

To determine

**To Find:** The proportion of people smile more than 80 times a day.

Explanation

**Given info:**

The random variable *X* denote the smiles and it follows the normal distribution with mean of

**Calculation:**

The formula for z score is,

Substitute the value 80 for *X*, 62 for

**(b)**

To determine

**To find:** The proportion of people smile at least 50 times a day.

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