Ex 6) A research firm conducted a survey to determine the mean
amount steady smokers spend on cigarettes during a week. They
found the distribution of amounts spent per week followed the normal
distribution with a population standard deviation of $5. A sample of
64 steady smokers revealed that x = 20
a.
What is the 95% confidence interval estimate of μ?
Ex 10) Use Appendix B.5 to locate the value of t under the following
conditions.
a. The sample size is 15 and the level of confidence is 95%
b. The sample size is 24 and the level of confidence is 98%
c. The sample size is 12 and the level of confidence is 90%
Ex 26) Past surveys reveal that 30% of tourists going to Las Vegas to
gamble spend more than $1,000. The visitor’s Bureau of Las Vegas
wants to update this percentage.
a.
The new study is to use the 90% confidence level. The estimate
is to be within 1% of the population proportion. What is the necessary
sample size?
b.
The bureau feels the sample size determined above is too large.
What can be done to reduce the sample? Based on your suggestions,
recalculate the sample size.
Ex 28) Forty-nine items are randomly selected from a population of
500 items. The sample mean is 40 and the sample standard deviation
9.
Develop a 99% confidence interval for the population mean