Answer:
With (a) confidence, the (b) (c) width of troughs is between (d) and (e) inches.
Q2
A survey is planned to determine the mean annual family medical expenses of employees of a large
company. The management of the company wishes to be 95% confident that the sample mean is
correct to within
±
$50 of the population mean annual family medical expenses. A previous study
indicates that the standard deviation is approximately $400.
a) How large a sample size is necessary?
b) If management wants to be correct to within
±
$25, what sample size is necessary?
Q3
If a quality control manager wants to estimate the mean life of light bulbs to within
±
20 hours with
95% confidence and also assumes that the population standard deviation is 100 hours, what sample
size is needed?