# MATHEMATICS

8) A random sample of 50 students has a test score average with a standard deviation of 11.4. Find the maximum error of estimate if c = 0.98. 8) ________

A) 3.76 B) 0.53 C) 1.61 D) 1.58

**SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.**

9) In a recent study of 71 eighth graders, the mean number of hours per week that they watched television was 18.7 with a standard deviation of 5.8 hours.

a) Find the 98% confidence interval of the mean.

b) If the standard deviation is doubled to 11.6, what will be the effect on the confidence interval? 9) ______________

**MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.**

10) A random sample of 150 students has a grade point average with a mean of 2.86 and with a standard deviation of 0.78. Construct the confidence interval for the population mean, m, if c = 0.98. 10) _______

A) (2.71, 3.01) B) (2.51, 3.53) C) (2.43, 3.79) D) (2.31, 3.88)

11) A random sample of 40 students has a test score with overbar(x) = 81.5 and s = 10.2. Construct the confidence interval for the population mean, m if c = 0.90. 11) _______

A) (78.8, 84.2) B) (51.8, 92.3) C) (66.3, 89.1) D) (71.8, 93.5)

12) A random sample of 40 students has a mean annual earnings of $3120 and a standard deviation of $677. Construct the confidence interval for the population mean, m if c = 0.95. 12) _______

A) ($2910, $3330) B) ($210, $110)

C) ($4812, $5342) D) ($1987, $2346)

13) A random sample of 56 fluorescent light bulbs has a mean life of 645 hours with a standard deviation of 31 hours. Construct a 95% confidence interval for the population mean. 13) _______

A) (636.9, 653.1) B) (539.6, 551.2)

C) (112.0, 118.9) D) (712.0, 768.0)

14) A group of 49 randomly selected students has a mean age of 22.4 years with a standard deviation of 3.8. Construct a 98% confidence interval for the population mean. 14) _______

A) (21.1, 23.7) B) (20.3, 24.5) C) (19.8, 25.1) D) (18.8, 26.3)

15) A group of 40 bowlers showed that their average score was 192 with a standard deviation of 8. Find the 95% confidence interval of the mean score of all bowlers. 15) _______

A) (189.5, 194.5) B) (186.5, 197.5)

C) (188.5, 195.6) D) (187.3, 196.1)

16) In a random sample of 60 computers, the mean repair cost was $150 with a standard deviation of $36. Construct a 99% confidence interval for the population mean. 16) _______

A) ($138, $162) B) ($18, $54) C) ($238, $274) D) ($537, $654)