Question

What sample size is needed if a ±1.5 lbs. margin of error is needed for computing the 95% confidence interval of the mean weight of U.S. adult males?  Assume a population standard deviation of 12 lbs.

Answer 1

Margin of Error (MOE) = 1.5

= 12 (population standard deviation)

Let n be the required sample size

For 95% confidence interval the level of significance () = 0.05

Critical value = = = = 1.960 (we get this value from z table and here we ignore the sign we only need the value)

sample size can not be in fraction so round off n

so, n = 246

Answer : The required sample size is 246