# Calculation of the size of a sample the the size of the population is unknown.

I am working with a colleague to produce a function to determine how frequently a widget should be pulled from a production line and evaluated for quality assurance. My colleague offered Cochran’s Sample Size Formula. This is very much a work in progress.

Where:

Z is the confidence level,

p is the probability of success or expected ratio,

q is the probability of failure and or (1-p)

d is the precision.

This web calculator was produced with JSCalc.io. The direct link to the calculator is: https://jscalc.io/calc/sEwlXFcMBNxnv6Zs.

References:

Sample Size in Statistics (How to Find it): Excel, Cochran’s Formula, General Tips