Reading proficiency:An educator wants to construct a

90%

confidence interval for the proportion of elementary school children in Colorado who are proficient in reading.

Part 1 of 3

(a) The results of a recent statewide test suggested that the proportion is

0.75

. Using this estimate, what sample size is needed so that the confidence interval will have a margin of error of

0.05

?

A sample of 1083 elementary school children is needed to obtain a 90% confidence interval with a margin of error of 0.05 .

Part:1 / 3

1 of 3 Parts Complete

Part 2 of 3

(b) Estimate the sample size needed if no estimate of

p

is available.

A sample of elementary school children is needed to obtain a 90% confidence interval with a margin of error of 0.05 .