RECENT STUDIES HAVE SHOWN THAT MAN IS MATHEMATICALLY INACCURATE AS AN INTUITIVE STATISTICIAN. IN AN ATTEMPT TO DETERMINE THE PARAMETERS OF PERCEIVED VARIABILITY, PILOT STUDIES WERE CONDUCTED WHICH INDICATED THAT THE COEFFICIENT OF VARIATION IS NOT A SUFFICIENT EXPLANATION AND THAT SS ALSO RELATE SEQUENCE EFFECTS TO VARIABILITY. IN THE 1ST STUDY, MEAN, STANDARD DEVIATION, AND LAMBDA (A MEASURE OF SEQUENCE EFFECTS) WERE INDEPENDENTLY MANIPULATED. IN THE 2ND STUDY, THE STANDARD DEVIATION AND LAMBDA WERE MANIPULATED UNDER INSTRUCTIONS TO IGNORE SEQUENCE EFFECTS. THE RESULTS SHOW THAT SEQUENCE EFFECTS ARE NOT ELIMINATED BY INSTRUCTIONS TO DISREGARD THEM. THE COMBINED RESULTS OF THESE STUDIES ARE DISCUSSED WITH RESPECT TO DECISION THEORY AND SUBJECTIVE PROBABILITY. (PsycINFO Database Record (c) 2006 APA, all rights reserved)