How to estimate the ideal sample size to validate failure rate in a process?

Question

Hello!

I have a factory process with a hypothesized failure rate of p=0.02, based on previous trials.

I would like to get the ideal sample size to validate if my process has a failure rate no larger than 0.02. How would you approach this?

Thanks in advance :)

Victor_G · Accepted Answer

Hello @PValueEnemy,

For this specific question, I would use one of the Calculators available in "Help", "Sample Index".
If you go into Teaching ressources, there is a panel for Calculators, and there is one calculator named "Sample Size for Confidence Interval".

When you open it, you specify that you are interested in "Proportion" :

And then you'll have to fill some informations so that the calculation can be done. For your specific problem, you need to specify the confidence level required, the planned value, and the desired margin of error. Here as an example, as soon as all windows have been filled, I obtain the calculated sample size needed :

More infos here : JMP Student Subscription

I hope this will help you,