Whenever something suddenly fell apart, my grandfather used to exclaim, “Down goes the meathouse!” I don’t know where that expression came from—as a child I often pictured a flabby house of raw meat caving in on itself. This was decades before Lady Gaga made wearing raw meat dresses... uh... fashionable?

My grandfather’s expression still pops into my head when I think about a probit analysis. A probit study is based on one very simple premise: Everything has its breaking point.

To illustrate this study, and to relive my childhood, I built some good old-fashioned card houses and tested how their roofs held up to stress loads of up to 50 U.S. quarters.

At each stress load, I tested 10 card houses and recorded how many collapsed. Here are the results, recorded in a Minitab worksheet:

Pretty simple, huh? The key thing to remember for this analysis is that the response variable is binary: The item fails (in this case, collapses), or it does not fail.

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