Chris Butterworth replied to the topic How to Verify a Problem Is Related to a Specific Test Environment? in the forum Tools & Templates 2 months ago
Have a look at the binomial distribution for n = 40 and p = 0.125. You can see that it is reasonable to observe 5 defects in a sample of 40.
But observing zero defects is improbable – it occurs less than 0.5% of the time.
I hope this is helpful.
Chris Butterworth replied to the topic Can You Do a Design of Experiments with Different Levels for Different Factors? in the forum Methodology 1 year, 2 months ago
Get a copy of Design and Analysis of Experiments by Douglas Montgomery. Chapter 5 will introduce you to factorial designs with some very good examples. What you are asking about is rather straightforward and well-explained in Montgomery’s book.