This article illustrates the difficulties of quantifying overconfidence in economic experiments and suggests a procedure for the development of the reliable overconfidence measurement instrument (test). Following the suggested two-stage procedure a sample measure of overconfidence is developed. First a pilot test is conducted to divide the initial fifty items into three difficulty levels: hard, moderate and easy questions. A final test was compiled of six questions of each difficulty levels. In the second phase a replicability check was run with the final instrument
