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You want to study the average time per day spent on using mobile phones by students...

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?

Math   Statistics-And-Probability   
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Answer #1

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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