Notes for use of the Sample Size Discrete Calculator:

- P is estimate of proportion for outcome of interest. Use P = 0.5 if unknown.
- Delta is desired proportion margin of error. Enter as the half-width, i.e. if the desired margin of error is +/- 3%, enter 0.03.
- Enter population size N to adjust for small populations (N < 10000).
- np should be >= 5. If necessary, reduce delta to adjust.
- Power (1 Beta) is not considered in these calculations. Power and Sample Size may be calculated using
**SigmaXL > Statistical Tools > Power & Sample Size Calculators**.

The challenge with this sample size calculator is that we need an estimate of the population proportion.This is a bit of a chicken and egg situation which comes first? I want to calculate an appropriate sample size to determine an outcome, but I am being asked to enter an estimate of the population proportion. First, keep in mind that this tool is a planning tool the true confidence intervals will be determined after you collect your data. Estimating the population proportion can be done if you have good historical data to draw from, for example, in historical customer surveys the percentage of satisfied customers was 80%. In this case you could use P=0.8. If you do not have

Notes for use of the Sample Size Continuous Calculator:

- Delta uses the same units as the standard deviation. Enter as the half-width, i.e., if the desired margin of error is +/- 0.25, enter 0.25.
- Enter (optional) population size N to adjust for small populations (N < 1000).
- Power (1 Beta) is not considered in these calculations. Power and Sample Size may be calculated using
**SigmaXL > Statistical Tools > Power & Sample Size Calculators**.

Here we need an

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