Sample size

How much data do you need before you decide? Choose what you want to find out; the tool works out the number.

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STEP 1

What do you want to find out?

Estimate an averageFor example the average lead time, within a margin.Estimate a percentageFor example the share of late orders, within a margin.Compare two averagesFor example lead time before and after a change, or on two lines.Compare two percentagesFor example the error rate before and after a change.

STEP 2

Your figures

Smallest difference that mattersIn the unit of the data: for example half a day.Standard deviation (from past data)Use the histogram tool on past data if you do not know it.Title (optional)