senior student

Question: A poll asked 1528 adults if they were in favor of the death penalty, 1238 said yes, find 99% confidence level for percent of all adult who are in favor of the death penalty.

Hi Kim,

Since n=1528 is very large, for confidence intervals for proportions we can use Z-test.

Estimation of proportion p=1238/1528 = 0.8102,
aplha/2 = (1-.99)/2=.005,
z(aplha/2)=2.575 (found by the table of areas under the standard normal probability distribution).

So confidence interval is

or in percent (78.4%, 83.6%)

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