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In: Statistics and Probability

You want to estimate the mean amount of time internet users spend on facebook each month....

You want to estimate the mean amount of time internet users spend on facebook each month. How many internet users must be surveyed in order to be 95% confident that your sample mean is within 15 minutes of the population mean? Based on results from a prior Nielsen survey, assume that the standard deviation of the population of monthly times spent on facebook is 210 min.

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Expert Solution

Standard Deviation ,   σ =    210                  
sampling error ,    E =   15                  
Confidence Level ,   CL=   95%                  
                          
alpha =   1-CL =   5%                  
Z value =    Zα/2 =    1.960   [excel formula =normsinv(α/2)]              
                          
Sample Size,n = (Z * σ / E )² = (   1.960   *   210   /   15   ) ² =   752.93
                          
                          
So,Sample Size needed=       753                  

orchestra answered 2 years ago
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