Question

Amanda earned a score of 940 on a national achievement test that was normally distributed. The mean test score was 850 with a standard deviation of 100

If 1000 students took the test, how many scored below Amanda? Use z table.

Answer 1

Lower than Amanda : 816 students.

Answer 2

lower than Amanda: 816 students

Explanation:

An equivalent way in which to state this problem is: Find the area under the standard normal curve to the left (below) 940.

Most modern calculators have built in distribution functions.

In this case I entered the single command normalcdf(-1000,940, 850, 100)

and obtained 0.816.

In this particular situation, this means that 0.816(1000 students) scored lower than Amanda: 816 students.