The possibility that "coder drift" may be a source of bias in classroom observation systems was investigated in two parallel experiments using the Flanders System of Interaction Analysis. Coder drift may be described as the differences in coding which result when observers create their own idiosyncratic systems of classifying teacher…

The results of two experiments support the hypothesis of "coder drift" which is defined as change that takes place while trained coders are using a system for a number of classroom observation sessions. The coding system used was a modification of the low-inference Flanders System of Interaction Analysis which calls for assigning…

Observer reliability and the confusability of codes, two sources of error in the collection of classroom observational data, are examined. Confusability is defined as the extent to which one code is mistakenly recorded as another code. Observational data were collected in each of 172 first grade and 171 third grade Follow Through and comparison…