Homework Help: Probability and Statistics

Posted by Kim on Sunday, April 29, 2012 at 8:09pm.

The ACT scores of applicants to college are approximately normally distributed with a mean of 20.3 and a standard deviation of 3.1. If a random sample of 20 applicants to college is chosen find the probability that their average ACT score will be 19 and 21.

Probability and Statistics - Anonymous, Sunday, April 29, 2012 at 10:35pm
68%!
Probability and Statistics - PsyDAG, Monday, April 30, 2012 at 12:01pm
Here is the method.

Z = (score-mean)/SEm

SEm = SD/√n

Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion related to the Z scores.

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