Variation in artifact recording introduced through the use of multiple observers is common in many archaeological projects. We report a study designed to assess random and systematic errors in nominal and ratio data recorded by observers on stone artifacts as part of a distributional study. A random sample of artifacts was selected and double analyzed, once by the regular observers and once by the project director. Random and systematic differences between the two sets of observations are assessed statistically. Analysis of these errors either permits corrections to be applied or indicates where care must be taken in analyzing artifact variation as a reflection of past human behavior.