Come again?

“HOW extremely stupid not to have thought of that!” Many statisticians, confronted with the GRIM test might find themselves echoing Thomas Huxley’s words when he read about the idea of natural selection. The GRIM test, short for granularity-related inconsistency of means, is a simple way of checking whether the results of small studies of the sort beloved of psychologists (those with fewer than 100 participants) could be correct, even in principle. It has just been posted in PeerJ Preprints by Nicholas Brown of the University Medical Centre Groningen, in the Netherlands, and James Heathers of Poznan University of Medical Sciences, in Poland.

To understand the GRIM test, consider an experiment in which participants were asked to assess something (someone else’s friendliness, say) on an integer scale of one to seven. The resulting paper says there were 49 participants and the mean of their assessments was 5.93. It might appear that multiplying these numbers should give an integer product—ie, a whole number—since the mean is the result of dividing one integer by another. If the product is not an integer (as in this…Continue reading
Source: Economist