## Question

A motor bike battery manufacturer found that the life of their batteries is normally distributed with a mean life span of 8700 hours and a standard deviation of 400 hours. If a battery is selected randomly, find the probability that the battery will last more than 9000 hours.

A. 0.773

B. 0.456

C. 0.227

D. 0.201

QUESTION 2

A motor bike battery manufacturer found that the life of their batteries is normally distributed with a mean life span of 8700 hours and a standard deviation of 400 hours. If a battery is selected randomly, find the probability that the battery will last less than 7600 hours.

A. 0.003

B. 0.012

C. 0.264

D. 0.359

QUESTION 3

An environmental service reported that a sample of 15 wild horses had a mean weight of 915 pounds with a sample standard deviation of 58 pounds. Calculate the margin of error, E, for a 99% confidence interval for the population mean weight µ of all wild horses.

A. 43.52

B. 41.25

C. 44.58

D. 36.52

QUESTION 4

The sampling distribution of sample means will more closely resemble the normal distribution as the sample size increases. What is the name given to this concept?

A. Descartes Rule of Signs

B. Central Limit Theorem

C. Empirical Rule

D. Mean Value Theorem

QUESTION 5

Assume that IQ scores are normally distributed with a mean of 100 and a standard deviation of 15. If a sample of 70 people are selected, find the probability that the mean IQ score of the sample is greater than 102.

A. 0.447

B. 0.132

C. 0.868

D. 0.553

QUESTION 6

Find the critical value tc for a 90% confidence level when the sample size is 12. Use Table 4 on page A10 (Appendix).

A. 1.796

B. 1.782

C. 3.106

D. 3.055

QUESTION 7

Find the area between z = -0.6 and z = 1.1 under the standard normal curve.

A. 0.410

B. 0.590

C. 0.726

D. 0.864

QUESTION 8

Find the area to the right of z = 0.85 under the standard normal curve.

A. 0.803

B. 0.402

C. 0.395

D. 0.197

QUESTION 9

In a survey of 6000 high school students, 3230 read books during the summer break. Using these sample statistics, find a 99% confidence interval for the proportion p of all high school students that read books during the summer break.

A. (0.516 , 0.560)

B. (0.521 , 0.554)

C. (0.528 , 0.547)

D. (0.485 , 0.591)

QUESTION 10

A computer repair service found that a random sample of 45 repair costs had a mean cost of $659. Assume that the population standard deviation is $125. Calculate the margin of error, E, for a 95% confidence interval for the population mean µ.

A. 48.07

B. 34.92

C. 30.55

D. 36.52

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