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Margin of Error Calculator


1) Margin of Error (Confidence Interval for Population Mean)


 
 
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All you need to know about Margin of Errors for Population Means

 Margin of Error Formula




Sample Margin of Error Problem


What is the Margin of Error when computing a 95% Confidence Interval for a population mean using a sample of bowling scores with mean x̄=200 and standard deviation σ=10 and sample size n=100 ?
Margin of Error
= z*σ/√(n)
= 1.96 * 10/√(100)
= 1.96 * 10/10
= 1.96*1
Finally, the Margin of Error for a 95% Confidence Interval is 1.96
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2) Margin of Error Calculator (Confidence Interval for Proportions)


 
 
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All you need to know about Proportion Confidence Intervals
Margin of Error for Proportion Confidence Interval




Sample Margin of Error Problem


What is the 95% Margin of Error for a Proportion Confidence Interval using a sample of students that have seen "Titanic" with x=20 favorable replies and sample size n=30 ?
Margin of Error = z*√(p̂*(1-p̂)/n)
= 1.96 * √((2/3*1/3)/30)
= 1.96 * √(2/270)
= 1.96 * 0.0861
Finally, the Margin of Error = .1688
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