t-test or z-test?

Choosing the correct hypothesis test is can be tricky as a new Six Sigma Green Belt or Black Belt. There are several flowcharts and videos to help you determine the correct path. The assumption of normality is important to understand if you find your data to be non-normal. It may be possible to apply parametric tests even if your data is non-normal.

Two of the more common tests used are the t-test and z-test which begin to look similar as the sample size increase and represents more of the population. Visit the t-distribution for more insight. 

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