In order to estimate the mean amount of time computer users spend on the interne

Question

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 90% confident that your sample mean is within 13 minutes of the population mean? Assume that the standard deviation of the population of monthly time spent on the internet is 210 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? O A. There may not be 707 computer users to survey. O B. It is difficult to precisely measure the amount of time spent on the internet, invalidating some data values. O C. The data does not provide information on what the computer users did while on the internet. O D. There are no obstacles to getting a good esitmate of the population mean.

Explanation / Answer

we use the following formula for margin of error(ME)
:
ME = z * s / square root(n) where z is the z-score we use to calculate the confidence interval, s is the standard deviation, n is sample size and ME is the desired margin of error
:
we want a 90% confidence interval(CI)
:
alpha(a) = 1 - (90/100) = 0.10
:
critical probability(p*) = 1 - (a/2) = 0.95

z-score associated with p* is 1.644853

13 = ((1.644853) * 210) / square root(n)

square root(n) = 345.41913 / 13

n = 706.0022 approximately 707

answer is A

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