Need to know b and c : picture available ; worth 10 points
1 answer:
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We have
425 corresponds to a z of
575 corresponds to
So we want the area of the standard Gaussian between -3/4 and 3/4.
We look up z in the standard normal table, the one that starts with 0 at z=0 and increases. That's the integral from 0 to z of the standard Gaussian.
For z=0.75 we get p=0.2734. So the probability, which is the integral from -3/4 to 3/4, is double that, 0.5468.
Answer: 55%