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Proportion Confidence Interval Calculator


 
 
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All you need to know about Proportion Confidence Intervals
Proportion Confidence Interval Formula




Sample 95% Proportion Confidence Interval Problem


What is the 95% Proportion Confidence Interval of your sample of students that have seen "Titanic" with x=20 favorable replies and sample size n=30 ?
CI-Setup: p̂ ± z*√(p̂*(1-p̂)/n)
Here, 20/30 ± 1.96 * √((2/3*1/3)/30)
2/3 ± 1.96 * √(2/270)
.6666 ± 1.96 * 0.0861
.6666 ± .1688
Finally, the 95% Proportion Confidence Interval is [0.4979 , 0.8355]
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