SOLUTION: The distribution of grades on a certain test has a mean of 85.5 with a standard deviation of 11.2. There are 400 tests. Assuming that the grades are normally distributed, predict t

Question 1161777: The distribution of grades on a certain test has a mean of 85.5 with a standard deviation of 11.2. There are 400 tests. Assuming that the grades are normally distributed, predict the number of students scoring between 75 and 95. Use a table of area under the curve within z standard deviations of the mean.
Round to the whole.
PLEASE SOLVE
Answer by Boreal(15235) (Show Source): You can put this solution on YOUR website!
z=(x-mean)/sd
=(75-85.5)/11.2=-0.9375
and 9.5/11.2=0.8482
the probability or area is 0.6276, so the number of tests would be 251 expected.
another way is 2nd VARS 2 normalcdf ENTER (75,95,85.5,11.2) ENTER*400=251
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