Homework 5a

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**1. What percent of the population fall between -1 and +3 standard deviations from the mean?**

a.100%

b.50%

c.20%

d.84%

**2. Carla is a 67 inch tall woman. What percentage of the population of women is shorter than Carla? (mean = 64.5, standard deviation =2.5)**

a. 1

b. 57

c. 34

d. 84

**3. For the following set of data, calculate the mean and standard deviation. Describe the mean and standard deviation in words after calculating it. **

a. The data set below gives the prices (in dollars) of cordless phones at an electronics store. What is the mean and standard deviation?

35, 50, 60, 60, 75, 65, 80

**4. Battery lifetime is normally distributed for large samples. The mean lifetime is 500 days and the standard deviation is 61 days. To the nearest percent, what percent of batteries have lifetimes longer than 561 days?**

Mean = 500 days and s.d. = 61 days.

Approximately what percent of batteries have lifetimes longer than 561 days?

**5. The number of children of each of the first 41 United States presidents is given in the accompanying table. For this population, determine the mean and the standard deviation to the nearest tenth.**

** How many of these presidents fall within one standard deviation of the mean?**

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