# Math-18 Statistic

## Math-18 Statistic

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Question 1

1. What requirements are necessary for a normal probability distribution to be a standard normal probability distribution?
 a. The mean is 1 and the standard deviation is 0. b. The mean is 0 and the standard deviation is 0. c. The mean is 0 and the standard deviation is 1. d. The mean is 1 and the standard deviation is 1.

1 points

#### Question 2

1. The area under the standard normal curve to the left of z = 1.34 is Blank 1 . (Round to four decimal places)

2 points

#### Question 3

1. The area under the standard normal curve to the right of z = -0.65 is Blank 1 . (Round to four decimal places)

2 points

#### Question 4

1. The area under the standard normal curve between z = -2.29 and z = -1.22 is Blank 1 . (Round to four decimal places)

2 points

#### Question 5

1. IQ scores for adults are normally distributed with a mean of 100 and a standard deviation of 15.  If an adult is chosen at random, what is the probability their IQ score is less than 90? (Change to z-score and use standard normal table.)

 a. 0.2514 b. 0.9525 c. 0.0475 d. 0.7486

1 points

#### Question 6

1. A safety light is designed so that the times between flashes are normally distributed with a mean of 3.50 seconds and a standard deviation of 0.50 seconds.  Find the probability that an individual time is greater than 4.50 seconds.
 a. 0.0228 b. 0.9821 c. 0.1587 d. 0.9772

1 points

#### Question 7

1. Women’s heights are normally distributed with a mean of 63.5 inches and a standard deviation of 2.5 inches.  What percentage of women are between 62 and 70 inches tall?  Blank 1 %  (Round to one decimal place)

2 points

#### Question 8

1. Find the z-scores for which 80% of the standard normal distribution’s area lies between -z and z.
 a. z = -1.28 and z = 1.28 b. z = – 1.96 and z = 1.96 c. z = – 0.84 and z = 0.84 d. z = -2.33 and z = 2.33

1 points

#### Question 9

1. Two high school students took equivalent language tests, one in German and one in French.  The student taking the German test, for which the mean was 66 and the standard deviation was 8, scored an 82, while the student taking the French test, for which the mean was 27 and the standard deviation was 5, scored a 35.  Use z-scores to compare the scores.
 a. A score of 82 with a mean of 66 and a standard deviation of 8 is better. b. The two scores are statistically the same. c. You cannot determine which score is better from the given information. d. A score of 35 with a mean of 27 and a standard deviation of 5 is better.

1 points

#### Question 10

1. The scores on a mathematics exam have a mean of 74 and a standard deviation of 8.  What is the score that corresponds to the 30th percentile?  Blank 1   (Round to two decimal places)

2 points

#### Question 11

1. Assume that blood pressure readings are normally distributed with a mean of 117 and a standard deviation of 5.  A researcher wishes to select people for a study but wants to exclude the top 10%.  What would be the largest reading that would still qualify the person for the study?
 a. 110.6 b. 123.4 c. 122.4 d. 132.9

1 points

#### Question 12

1. Assume that human body temperatures are normally distributed with a mean of 98.21º F and a standard deviation of 0.61º F.  Find the temperature at the third quartile.  This means 75% of the temperatures are below this point.

Blank 1 º F   (Round to two decimal places)

2 points

#### Question 13

1. Men’s heights are normally distributed with a mean of 69.0 inches and a standard deviation of 2.8 inches.  The U.S. Marine Corps requires that men have heights between 64 inches and 78 inches.  Find the percentage of men that meet this requirement.  Blank 1 %  (Round to two decimal places)

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