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T08-01 1 Population Sample Size Calculations

Purpose Allows the analyst to analyze the sample size necessary to conduct "statistically significant" testing for sample mean and proportion situations for a 1- confidence level and "allowable error".

Inputs Confidence levelMargin of error Population/Sample standard deviation

Outputs Sample size

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- 3sd -2sd -1sd + 1sd + 2sd + 3sd

Margin of Error - Means Margin of Error - Proportions

Determining How Many Samples to Take

Z2

Level of Confidence

Depends on the level of confidence (1-)?

Ε

σ)(Z=n

2

22α/2

Ε

π)-π(1)(Z=n

2

2α/2

n

Z=E /2

n

π)-π(1Z=E α/2

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Sample Size for Mean - Example

Calculate the sample size necessary to ensure that you are 95% confident that the error is within 2 of the population mean when the population standard deviation is 6.82.

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Input the confidence level (.XX for XX%), Std Dev, and Margin of Error.

The Sample Size necessary to achieve this accuracy is automatically calculated.

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Sample Size for Proportion - Example

Calculate the sample size necessary to ensure that you are 95% confident that the error is within .10 of the population proportion when the sample population proportion is .80.

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Input the confidence level (.XX for XX%), proportion, and Margin of Error.

The Sample Size necessary to achieve this accuracy is automatically calculated.