Question

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In order to estimate the mean amount of time computer users spend on the internet each month, how many users must be surveyed in order to be 90% confident that your sample mean is within 14 minutes of the population mean? Assume that the standard deviation of the population of monthly time spent on the internet is 206 min.
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The minimum sample size required is _________computer users.

Answer 1

Given that,

Standard deviation = = 206

Margin of error = E = 14

At 90% confidence level the z is ,

= 1 - 90% = 1 - 0.90 = 0.10

/ 2 = 0.10 / 2 = 0.05

Z_/2 = Z_0.05 = 1.645

Sample size = n = [(Z_/2 * ) / E]²

= [(1.645 * 206) / 14]²

= 585.8

Sample size = 586

The minimum sample size required is 586 computer users.