Question

An instructor gives a 100 point examination in which the grades are normally distributed. The mean is 70 and the standard deviation is 10. If there are 1%A+ . find the lowest possible score to get A+?

Answer 1

Let the lowest possible score to get an A+ be x.

Let X be a random variable defining the scores.

The probability that X will be greater than x should be equal to 1%.

Or,

the z score corresponding to a p-value of 0.01 is 2.33

So,

Hence, in order to get an A+, the lowest score should be 93.3.

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