SOLUTION: The scores on a test is normally distributed with a mean of 100 and a standard deviation of 11. What is the probability that a score will be between 97 and 125?

Question 1061809: The scores on a test is normally distributed with a mean of 100 and a standard deviation of 11. What is the probability that a score will be between 97 and 125?
Answer by Edwin McCravy(20059) (Show Source): You can put this solution on YOUR website!

On your TI-83 or TI-84

normalcdf(97,125,100,11), read .595947231, Press ENTER

To find "normalcdf(" on your calculator, press 2ND then 2

If your teacher won't allow calculator work, find z-scores
for the endpoints:



 and 

If your table contains negative z values, look up z=-0.27 
(the closest you can get to -.2727, and read 0.3936, and 
look up z=2.27, (the closest you can get to 2.2727 and read 
0.9884.

Subtract and get 0.9884-0.3936 = 0.5948.

If your table contains only positive z values, look up z=0.27 
(the closest you can get to .2727, and read 0.1064, and look 
up z=2.27, (the closest you can get to 2.2727 and read 0.4884.

Add and get 0.1064+0.4884 = 0.5948.

The calculator value 0.595947231 is more accurate, since we 
don't have to round off the z-scores when we use the 
calculator.

[It's a shame that teachers and books still require old-fashioned
inaccurate tables when technology is available so freely.]

Edwin

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