Re: Finding a probability from a Mean and a Standard Deviation
I think you are meant to assume that weight at a given age is reasonably close to a Normal distribution, at least near the center. I doubt that is true, I would expect a bimodal distribution for boys and girls, and significant distortions for ethnicity, nutrition and certain medical conditions. Moreover, "five year old" probably means a group distributed in age from five to six.
However, to do the calculation if the distribution were Normal, you compute the probability of a standard Normal variate being less than 0.99 (8/8.1) standard deviations above the mean. You can do that with a table, or in Excel with Normdist(70,62,8.1,True) = 0.8383. That's probably not a bad answer for the actual data.
It's also possible this is a trick question and you are meant to answer that it cannot be determined with the information given.
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