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Essentials of Statistics for the B...

8th Edition
Frederick J Gravetter + 1 other
ISBN: 9781133956570

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BuyFindarrow_forward

Essentials of Statistics for the B...

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.

  1. a. What proportion of people smile more than 80 times a day?
  2. 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 μ=62 time per day and standard deviation of σ=18.

Calculation:

The formula for z score is,

z=Xμσ

Substitute the value 80 for X, 62 for μ and 18 for σ.

z=806218=1818=1

(b)

To determine

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

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