10. What is the 98% interval estimate of u given s = 3, n=15 and x =18.
C. 15.97 < u < 20.03
A. 15.57 < u < 20.53
D. 14.97 < u < 21.03
B. 14.97 < u < 21.03
11. A sample of 50 learners showed a mean height of 60 inches. If it is known
that the standard deviation of heights of learners is 2.5 inches, what is the
70% confidence interval estimate for the height of all the learners?
A. 59.64 < u < 60.36
C. 59.32 < u < 60.48
B. 58.52 < u < 61.48
D. 59.52 < u < 62.48
12. A random sample of 12 graduates of a certain secretarial school typed an
average of 73.9 words per minute (wpm) with a standard deviation of 8.7
wpm. Assuming that the number of words typed per minute is approximately
normally distributed, what is the 95% interval for the average number of
words typed by all the graduates of this school.
A. 58.52 < u < 61.48
C. 68.52 < u < 79.48
B. 68.52 < u < 79.48
D. 68.37 < u < 79.43
13. Given a standard deviation of 10.4, confidence interval of mean 95% and a
margin of error or maximum allowable deviation of 4.35, what is the
appropriate sample size?
A. 19
B. 20
C. 21
D. 22
14. Twenty packages of mangoes are inserted in a box for shipment. To test the
weight of the boxes, a few were checked. The mean weight is 9.3 kg, with a
standard deviation of 0.23 pounds. How many boxes must the processor
sample to be 95% confident that the sample mean does not differ from the
po ulation mean by more than 0.1 kg?
A. 19
B. 20
C. 21
D. 22
15. A college dean wishes to estimate the average number of hours students
spend doing homework per week. The standard deviation from a previous
study is 4.5 hours. How large a sample must be selected, if he wants to be
95% confident of finding whether the true mean differs from the sample
mean by 2.1 hours?
A. 16
B. 17
C. 18
D. 20​