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The Sample Size Estimator can assist you in your quant study designs by giving an estimate of a necessary sample size based on a desired level of precision, the estimated standard deviation of your study, the expected range of measuremetns, and  your desired confidence interval.

To use the estimator, input the following parameters into the spinners and slider on the left below:

• The desired level of precision
• (Expected) Standard deviation (s)
• The lagest measurement (Max Value) you would expect
• The smallest measurement (Min Value) you would expect
• The level of confidence you desire for this study (this tool doesn't work at less than 80% CL)

As you adjust these inputs you can observe the effect on study outputs to the right:

• The vertical bar shows the max and min study value with growing and shrinking error bars around a midpoint value to show the relative size of the confidence interval to the range of expected data.
• The box to the right displays the sample size needed to achieve your desired study outcomes.

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Updated July 28, 2010