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 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 191 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 see required is computer users. (Round up to the nearest whole number)

Explanation / Answer

Note that      
      
n = z(alpha/2)^2 s^2 / E^2      
      
where      
      
alpha/2 = (1 - confidence level)/2 =    0.025  
      
Using a table/technology,      
      
z(alpha/2) =    1.959963985  
      
Also,      
      
s = sample standard deviation =    191  
E = margin of error =    12  
      
Thus,      
      
n =    973.1962447  
      
Rounding up,      
      
n =    974   [ANSWER]

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