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The results from a statistics class' first exam are as follows: The mean grade obtained by...

The results from a statistics class' first exam are as follows: The mean grade obtained by its 25 students is 83, with a standard deviation of 11. The distribution of grades was unimodal and symmetrical. What is the probability that a student received a grade above 90?

The results from a statistics class' first exam are as follows: The mean grade obtained by its 25 students is 83, with a variance of 121.  The distribution of grades was unimodal and symmetrical. What z score is required to be in the bottom 20%?

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