Exercises. 1. Determine the sample size for the estimate of for the following:

1. Determine the sample size for the estimate of for the following:

a) ; ; confidence level = 99%

b) ; ; confidence level = 95%

c) ; ; confidence level = 90%

2. Determine the most conservative sample size for estimation of the population proportion for the following:

a) ; confidence level = 99 %

b) ; confidence level = 96 %

c) ; confidence level = 90 %

3. A sample of 50 workers’ average weekly earnings gave . Determine the sample size that is needed for estimating the population mean weekly earnings with a 98 % error margin of $ 3.50.

4. How large a sample should be taken to be 95 % sure that the error of estimation does not exceed 0.02 when estimating a population proportion?

5. A food service manager wants to be 95 % confident that the error in the estimate of the mean number of sandwiches dispensed over the lunch hour is 10 or less. What sample size should be selected if

6. One department manager wants to estimate at 90 % confidence level the mean amount spent by all customers at this store. He knows that the standard deviation of amounts spent by customers at this store is $ 27. What sample size he chooses so that the estimate is within $ 3 of the population mean?

7. A teacher wants to estimate the proportion of all students who own mobile telephones. How large should the sample size be so that the

99 % confidence interval for the population proportion has a maximum

error of 0.03?

8. A private university wants to determine a 99 % confidence interval for the mean number of hours that students spend per week doing homework. How large a sample should be selected so that the estimate is within 1 hour of the population mean? Assume that the standard deviation for the time spent per week doing homework by students is 3 hours.

Дата добавления: 2015-08-05