Statistics Review Normal Distribution

What shape is a normal distribution curve?

• Half curve

• Round curve

• Bell curve

• Square curve

The mean life of a tire is 30,000 km. The standard deviation is 2000 km.

Then, 68% of all tires will have a life between ___________ km and __________ km.

•  28,000 km and 32,000 km.

• 24,000 km and 34,000 km.

• 26,000 km and 34,000 km.

• 27,000 km and 31,000 km.

A fifth grader takes a standardized achievement test (mean = 125, standard deviation = 15) and scores a 148.  What is the fifth graders standardized score?

• 2.2

• 2.75

• 139.67

• 1.53

If the shaded area under the curve is .85, what is the other missing portion of the curve?

• .26

• .15

• .30

• .17

What percentage of the data is between 40 and 90?

• 25 %

• 50%

• 75%

• 100%

What percentage of the data is between 40 and 150?

• 25 %

• 50%

• 75%

• 100%

The distribution of the scores on the last test is normally distributed with a mean of 82, and approximately 68% of the scores are between 77 and 87. What is the approximate standard deviation of the scores?

• 2

• 3

• 4

• 5

The heights of American men aged 18 to 24 are approximately normally distributed with a mean of 68 inches and a standard deviation of 2.5 inches. About what percentage of the men are over 70.5 inches tall?

• 2.5%

• 84%

• 16%

• 97.5%

Jack and Jill are both enthusiastic players of a certain computer game. Over the past year, Jack’s mean score when playing the game is 12,400 with a standard deviation of 1500. During the same period, Jill’s mean score is 14,200, with a standard deviation of 2000. They devise a fair contest: each one will play the game once, and they will compare z-scores. Jack gets a score of 14,000, and Jill gets a score of 16,000. What were each of their z-scores?

• Jack: 1.07, Jill: 0.95

• Jack: 1.067, Jill: 0.90

• Jack: 1.07, Jill: 0.91

• Jack: 1.33, Jill: 0.98

A study of elite distance runners found a mean body weight of 60 kilograms (kg), with a standard deviation of 6 kg. Assuming that the distribution of weights is approximately normal. What percentage of runners have body weights below 54 kg?

• 10%

• 25%

• 16%

• 75%