Statistical and Practical Significance (3 of 4)

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The experimenter presented this conclusion to management but management did not accept it. The color displays were so dazzling that despite the statistical analysis, they could not believe that color did not improve performance by at least 10 seconds. The experimenter decided to do the experiment again, this time using 100 subjects for each type of display. The results of the second experiment were very similar to the first. Subjects were slightly faster at making reservations on a color display (M = 504.7 seconds) than on a black and white display (M = 508.1 seconds) . This time the difference was significant at the 0.01 level rather than the 0.05 level found in the first experiment. Despite the fact that the size of the difference between means was no larger, the difference was "more significant" due to the larger sample size used. If the population difference is zero, then a sample difference of 3.4 or larger with a sample size of 100 is less likely than a sample difference of 3.5 or larger with a sample size of 50.