T for 2

Should I use a paired t or a two-sample t?

Boxers or briefs. Republican or Democrat. Yin or yang. Why is it that life often seems to boil down to two choices?

Heck, it even happens when you open the Basic Stats menu in Minitab. You’ll see a choice between a two-sample t-test and a paired t-test:

Which test should you choose? And what’s at stake?

Ask a statistician, and you might get this response: “Elementary, my dear Watson. Choose the two-sample t-test to test the difference in two means: H0: µ1 – µ2 = 0. Choose the paired t-test to test the mean of pairwise differences H0: µd = 0.”

You gaze at your two sets of data values, mystified. Do you have to master the Greek alphabet to choose the right test?

όχι !

(That’s Greek for “no.”)

Base your decision on how the data are collected

Dependent samples: If you collect two measurements on each item, each person, or each experimental unit, then each pair of observations is closely related, or matched.

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Comments

t 4 2

Or 2 4 t? May be that your question cannot be answered by a two-sided answer, that is, go right or go left, go up or go down, but by a multiple answer, instead. May be that we should instead ask ourselves "why" y is plotted against x, and not how: this approach could help us to better understand a world that is nor black neither white, but it is colored an infinite number shades of grey.