You want to study the average time per day spent on using mobile phones by students at an university. Your goal is to provide a 95% confidence interval estimate of the mean time per day. Previous studies suggest that the population standard deviation is about 4 hours per day. What sample size (at a minimum) should be used to ensure the the sample mean is within
(a) 1 hour of true population mean?
(b) 0.5 hour of true population mean?
Given that, population standard deviation = 4 hours
A 95% confidence level has significance level of 0.05 and critical value is,
We want to find, the sample size ( n ), for following margin of errors,
a) For margin of error ( E ) = 1 hour
Therefore, required sample size is 62
b) For margin of error ( E ) = 0.5 hour
Therefore, required sample size is 246
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