Kitchen appliances don’t last forever. The lifespan of all microwave ovens sold in the United States is approximately Normally distributed with a mean of 9 years and a standard deviation of 2.5 years. What percentage of the ovens last more than 10 years?

• 11.5%

• 34.5%

• 65.5%

• 69%

• 84.5%

The following statistics were produced at the end of a week at a weight loss center indicating pounds lost.

 

Mean = 5 lbs                           Median = 7 lbs                                    Mode = 4 lbs

First Quartile = 2 lbs               Third Quartile = 8.5 lbs                      Standard Deviation = 0.5 lbs

 

Which of the following statement(s) are correct?

 

I. One quarter of weight watchers lost 2 pounds or less.

II. The middle 50% of the weight waters lost between 2 and 8.5 pounds.

III. The most common weight loss waas 4 pounds.

• I only

• II only

• III only

• I and III

• I, II, and III

The distribution of weights of female college cross-country runners is approximately normal with mean 122 pounds and standard deviation 8 pounds. Which of the following is closest to the percent of the runners who weigh between 114 pounds and 138 pounds?

• 18%

• 32%

• 68%

• 82%

• 95%

A student obtained a z-score of -1.40 on a national test for which the mean score was 500 and the standard deviation was 50. The student’s actual test score was

• 570

• 430

• 564

• 640

• 450

The mean age (at inauguration) of all U.S. Presidents is approximately Normally distributed with a mean of 54.6.  Barack Obama was 47 when he was inaugurated, which is the 11th percentile of the distribution.  Which of the following is closest to the standard deviation of presidents’ ages?

• -9.20

• -6.18

• 6.18

• 7.60

• 9.20

A different species of cockroach has weights that follow a Normal distribution with a mean of 50 grams. After measuring the weights of many of these cockroaches, a lab assistant reports that 14% of the cockroaches weight more than 55 grams. Based on this report, what is the approximate standard deviation of weights for this species of cockroaches?

• 4.6

• 5.0

• 6.2

• 14.0

• cannot be determined

This data is normally distributed.  What percent of the data is in the shaded region?

• 68%

• 95%

• 99.7%

• 50%

This data is normally distributed.  What percent of the data is in the shaded region?

• 68%

• 95%

• 99.7%

• 50%

The monthly income of 5000 workers at the Microsoft plant are distributed normally. Suppose the mean monthly income is $1250 and the standard deviation is $250.
Creating a normal distribution curve shows that the percentage of workers who earn between $750 and $1500 per month is ​ (a)  

• 800 workers

• 125 workers

• 81.5% of workers

• 97.5% of workers

This data is normally distributed.  What percent of the data is in the shaded region?

• 68%

• 95%

• 99.7%

• 50%