OK, try me, i am not sure if my answer is correct 68% 1 standard deviation interval 95% 2 standard deviation interval 99.7% 3 standard deviation interval
i think here in this question, we are seeking a approximate number so 99% is approximate can be used for 99.7% (480-355)/3=(355-230)/3
发表于 2009-6-3 11:17
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