McNemar Test

The NcNemar Statistical Test

The McNemar test is a nonparametric statistical test to compare dichotomous (unique) results of paired data.

If you are comparing survey results (favorable/unfavorable) for a group of potential customers given two ad campaigns, or evaluating the performance of two vendors in a set of prototype units, or determining if a maintenance procedure is effective for a set of equipment, this test permits the detection of changes.

The McNemar test is similar to the χ2 test. The McNemar only works with a two by two table, where the χ2 test works with larger tables. The χ2 test is checking for independence, while the McNemar test is looking for consistency in results.

Let’s examine an example where a group of people are surveyed about a prototype design, before and after a presentation.

The Question

We want to know if the presentation is effective in changing people’s mind about their opinion concerning a new product concept.

Some people in the group will be favorable before and after the presentation, and some will be hold an unfavorable opinion before and after the presentation. Some will change their opinion, randomly, and some will or could be influenced by the presentation. We want to know if the number of people that…