for a certain exam,a score of 58 was 2 standard deviations below the mean and a score of 98 was 3 standard deviations above the mean .what was the mean score for the exam

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foracertainexam,ascoreof58was2standarddeviationsbelowthemeanandascoreof98was3standarddeviationsabove

for a certain exam,a score of 58 was 2 standard deviations below the mean and a score of 98 was 3 standard deviations above the mean .what was the mean score for the exam
for a certain exam,a score of 58 was 2 standard deviations below the mean and a score of 98 was 3 standard deviations above the mean .what was the mean score for the exam

for a certain exam,a score of 58 was 2 standard deviations below the mean and a score of 98 was 3 standard deviations above the mean .what was the mean score for the exam
58小于平均数有2个标准差,即x-58=2z
98大于平均数有3个标准差,即98-x=3z
将x=58+2z代入98-x=3z解得:z=8
所以x=58+2x8=74

98-58=40 40/(2+3)=8
58+ 16 =74.
问题是58分比mean 底两个standard deviations (标准偏差), 98 比mean 多3个, 所以=58+(98-58)/5 x2