Then use these guidelines to check it for measurement effectiveness. When category frequency is low, then the step difficulty is poorly estimated and unstable. Irregularity in category observation frequency signals irregularity in usage. Look for unimodal use or peaking in a central or extreme categories. Average category measures advance.
Average measures are an empirical indicator of the context in which the category is used.
Since higher categories are intended to reflect higher measures, then the average measures are expected to advance. Outfit mean-squares less than 2.0. We model a definite amount of randomness in choosing categories. This amount is indicated by a mean-square of 1.0. Values over 2.0 indicate that there is more unexpected than expected randomness.