Instructions
This calculator estimates the number of replicates to calculate confidence limits with a specified precision.
The degrees of freedom for a standard deviation is the number of replicates minus 1. For example, if you make 3 measurements, the degrees of freedom for the standard deviation is 2.
The standard deviation comes from previous data. You will need to run a few replicates (3 to 5) to determine an estimate.
The precision comes from your engineering judgement. It is specified as half the confidence interval width. If you want confidence of plus or minus 0.5, 0.5 is half the confidence interval width.
Confidence Limit
Sample Size Calculator
Please enter the standard deviation, the associated degrees of freedom, and half the width of the confidence interval desired.
The sample size is for each mean.
