different findings emerge when observed and self-reported procrastination are compared. steel et al. constructed their own scales based on silver and sabini's "irrational" and "postponement" criteria. they also sought to measure this behavior objectively. during a course, students could complete exam practice computer exercises at their own pace, and during the supervised class time could also complete chapter quizzes. a weighted average of the times at which each chapter quiz was finished formed the measure of observed procrastination, whilst observed irrationality was quantified with the number of practice exercises that were left uncompleted. researchers found that there was only a moderate correlation between observed and self-reported procrastination (r = 0.35). there was a very strong inverse relationship between the number of exercises completed and the measure of postponement (r = −0.78). observed procrastination was very strongly negatively correlated with course grade (r = −0.87), as was self-reported procrastination (though less so, r = −0.36). as such, self-reported measures of procrastination, on which the majority of the literature is based, may not be the most appropriate measure to use in all cases. it was also found that procrastination itself may not have contributed significantly to poorer grades. steel et al. noted that those students who completed all of the practice exercises "tended to perform well on the final exam no matter how much they delayed."