Detecting a change or difference is often the aim of an experiment or set of measurements. We want to learn which vendor, process, or design provides a better result.

When we use a sample to estimate a statistic for a population we take the risk that the sample provides values that are not representative of the population. For example, if we use a professional basketball team to sample men’s height. We may conclude that the height of men in the general population is taller than the true population value. [Read more…]

One of the most often asked questions of reliability professionals (or statisticians) is related to how many samples for a test? This typically is not an easy question to resolve without some work and knowledge of the testing in question. We are often asked anyway, and expected to have an answer.

While not the most often asked question on the CRE exam, you might see something related. Budget planning, prototype counts, test equipment sizing, etc. all need an estimate for sample size. [Read more…]