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    • Thread Starter

    The 25 children in a class each roll a fair die 30 times and record the number of sixes they obtain. Find an estimate of the probability that the mean number of sixes recorded for the class is less than 4.5.

    How can I find the sample mean and standard deviation?
    • PS Helper

    PS Helper
    It might help to use the fact that \bar X = \dfrac{1}{n} \displaystyle \sum_{i=1}^n X_i. In this case, n=25 and X_i is the number of 6s obtained in 30 rolls of a die, so each X_i is binomially distributed (and you can assume they're independent).
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