Brian P.

asked • 06/07/21

Find probabilities using Normal Distribution

Mean= 51 SD= 22 P(45 and 57)


(45-51)/22= -0.2727

(57-45)/22= 0.2727


Z chart 0.272= .9967


1-.9967= .0033

1-2(.0033)= 0.9934


I thought this was correct, but the answer is .215

Where did I make an error?



Mark M.

What do you mean by P(45 and 57)?
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06/07/21

Philip P.

tutor
You computed the z-scores correctly (although the second one is (57-51)/22 = 0.2727...) and computed the probability correctly; however you read the z chart incorrectly. If you go back and read off the correct percentile values from the chart, you'll get the right answer.
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06/07/21

1 Expert Answer

By:

Anthony T. answered • 06/07/21

Tutor
5 (53)

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