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The Confidence Interval Estimator can assist you in your quant study designs by giving an estimate of a confidence interval around study measurements based on sample size, 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:

• Sample size (n)
• (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 gauge shows the confidence interval as a percentage of the measured value: less than 5% is "green", 5-10% is "yellow", and more than 10% is "red".
• The box below the gauge displays the actual confidence interval in study units.

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Updated July 28, 2010