GMAT Prep 70 75 80 85 90 105 105 130 130 130 The list shown consists of the time, in seconds, that it took each of 10 school children to run a distance of 400 meters. If the standard deviation of the 10 running times is 22.4 seconds, rounded to the nearest tenth of a second, how many of the 10 running times are more than 1 standard deviation below the mean of the 10 running times?
Anybody knows wut does "1 standard deviation below the mean of the 10 running times" mean here?
mean=100 the range of one standard deviation is 100+-22.4=77.6-122.4 The number below the mean is 70, 75, 80, 85, 90 and more than 1 standard deviation is those smaller than the range above: 70, 75 so the number is TWO PS, be sure the conception that the number "more than 1 standard deviation " is those smaller than the range of one standard deviation
the conception that the number "more than 1 standard deviation " is those smaller than the range of one standard deviation or those bigger than the range of one standard deviation. You may refer the pic of deviation.
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发表于 2011-1-28 02:40:21
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