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The List consist of the times in seconds that took each of the schoolchildren to run a distance of 400 meters. If the standard deveiation 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 one standard deviation below the mean of the 10 running times?
Answer is two, but i dont know how to calcualte this one though it looks simple
... Pleae help me .. have exam in next 3 weeks.