In order to estimate the mean amount of time computer users

In order to estimate the mean amount of time computer users spend on the internet each month, how many computer users must be surveyed in order to be 95% confident that your sample mean is within 12 minutes of the population mean? Assume that the standard deviation of the population of monthly time spent on the internet is 208 min. What is a major obstacle to getting a good estimate of the population mean? Use technology to find the estimated minimum required sample size.

The minimum sample size required is (___) computer users.

(Round up to the nearest whole number.)

What is a major obstacle to getting a good estimate of the population mean?

A) there may not be 1,155 computer users to survey

B)It is difficult to precisely measure the amount of time spent on the internet, invalidating some data values

C)The data does not provide information on what the computer users did while on the internet.

D)There are no obstacles to getting a good estimate of the population mean

Solution

Compute Sample Size
n = (Z a/2 * S.D / ME ) ^2
Z/2 at 0.05% LOS is = 1.96 ( From Standard Normal Table )
Standard Deviation ( S.D) = 208
ME =12
n = ( 1.96*208/12) ^2
= (407.68/12 ) ^2
= 1154.187 ~ 1155