A simple and intuitive test for number-inflation or number-deflation.

We present a test of zero-modification which checks if the number of zeros is consistent with the hypothesized count distribution. This test is easily extended to test for inflation or deflation of any non-negative values, and, by performing multiple tests of inflation/deflation of the counts present in observed data relative to any given model, it is possible to assess the suitability of that model. Such multiple testing may be represented diagrammatically. The test for number-inflation/deflation is informally called the “Christmas Eve Test” as the original idea occurred to the main author on December 24th, 2014, and the diagrammatic method the “Durham Diagram” as it was developed during preparation for a talk at Durham University.