Solution :
Given that,
Point estimate = sample proportion = = x / n = 25 / 125 = 0.20
1 - = 1 - 0.20 = 0.80
Z/2 = Z0.005 = 2.576
Margin of error = E = Z / 2 * (( * (1 - )) / n)
= 2.576 (((0.20 * 0.80) / 125)
= 0.092
A 99% confidence interval for population proportion p is ,
± E
= 0.20 ± 0.092
= ( 0.108, 0.292 )
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