Editor's note: Terry Grapentine is an independent marketing research consultant based in Ankeny, Iowa.

In our recent book, Critical Thinking for Marketers: Learn How to Think, Not What to Think, my co-authors David Dwight, David Soorholtz and I focused on helping marketers reason more clearly but the book’s topics are equally useful to marketing researchers. In particular, researchers’ application of critical thinking skills not only helps them reason more clearly about marketing research issues but places them in a more valuable position to help the marketers they serve make better marketing decisions.

In part, the book describes 60 logical fallacies, which are errors in reasoning, in the context of real-world vignettes, drawn from our own experiences. The discussion below presents three such vignettes: Affirming the Consequent, the Ludic Fallacy and Appeal to Possibility.

Affirming the Consequent

Location: Off-site meeting between HR and the sales department.

Issue: HR and sales force management are reviewing the results of a sales-training system the company has had in place for 18 months.

Tom (human resources VP): “My department has reviewed the sales force’s performance before and after we deployed the new training system. Sales are up and I, for one, would attribute that to the new training system. What do you think, Brian?”

Brian (sales VP): “Well, we spent a lot of time screening different training system companies and it seems we selected the right one. I vote that we continue with the program.”

Tom: “I agree, Brian.”

Tom and Brian are assuming that the improved performance of the sales force can be attributed to the training program and their inference seems reasonable. If the sales training program is effective and all other factors are held constant, sales would increase. Sales increased; therefore, the sales training program has been effective. This c...