Exam grades: scores on a statistics final in a large class were normally distributed with a mean of 75 and a standard deviation of 9.Part D: Between what two values are the middle 60% of the scores?*Need help with figuring out how to find the two values you plug in for the area of invNorm to get the final answer on a TI-84.

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Asked Jul 8, 2019
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Exam grades: scores on a statistics final in a large class were normally distributed with a mean of 75 and a standard deviation of 9.

Part D: Between what two values are the middle 60% of the scores?

*Need help with figuring out how to find the two values you plug in for the area of invNorm to get the final answer on a TI-84.

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Expert Answer

Step 1

Let X be the scores on statistics final, which is normally distributed with mean = 75 and standard deviation = 9.

It is known that, in a normal distribution, there is equal area above and below the mean value.

Thus, P(X > 75) = 0.5 and P(X < 75) = 0.5

 

It is required to find the x values such that, P(x1 < X < x2) = 0.60

As the area covered is middle 60%, P(x1 &...

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X2 75 X1 20% 60%

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