Question

What sample size is needed to estimate the proportion of highway speeders within 5 percent using a 90 percent confidence level?

		68
		271
		165
		385

Answer 1

The population proportion is not given, so we assume population proportion to be 50% or 0.50 in all cases where the population proportion is not given.

so, we have p = 0.50

margin of error(ME) = 5% or 5/100 = 0.05

z score for the 90% confidence interval is 1.645

Using the formula

sample size(n) =

setting the given values, we get

sample size(n) =

Rounding it to nearest integer, we get 271

so, the required sample size is n = 271

option B is correct answer