Question

) In a study of TV viewing habits, it is desired to estimate the average number of hours that learners spend

watching per week. If it is reasonable to assume that

  3.2

hours, how large a sample is needed so that it

will be possible to assert with 95% confidence that the sample mean is off by less than 20 minutes? �

Answer 1

$Given~\sigma=4.8hours\\ |X-\mu|<1.96\times\frac{4.8}{\sqrt{n}}\\ 1.96\times\frac{4.8}{\sqrt{n}}>\frac{1}{3}\\ \frac{9.408}{\sqrt{n}}>\frac{1}{3}\\ \frac{1}{\sqrt{n}}>\frac{1}{28.224}\\ n=28.224^2\\ n=796.59$