SOLUTION: Students at Arrowhead High School took a Math test with a mean of 120 and a standard deviation of 25. Approximately, __ % of the students scored above 170.

Algebra ->  Finance -> SOLUTION: Students at Arrowhead High School took a Math test with a mean of 120 and a standard deviation of 25. Approximately, __ % of the students scored above 170.      Log On


   

Question 1162147: Students at Arrowhead High School took a Math test with a mean of 120 and a standard deviation of 25. Approximately, __ % of the students scored above 170.
Answer by Theo(13342) About Me  (Show Source):
You can put this solution on YOUR website!
the mean is 120.
the standard deviation is 25.

what % of the students scored above 170?

use the z-score formula of z = (x-m)/s
formula becomes:
z = (170 - 120) / 25
solve for z to get:
z = 50 / 25 = 2.0
look up z-score in z-score table to find that the area to the left of that z-score is equal to .97725
since you want the percent of students who scored above that z-score, then take 1 - .97725 to get the area to the right of that z-score equal to get .02275.

multiply that by 100 to get 2.275% of the students scored above 170.

here's the table i used.

https://www.math.arizona.edu/~rsims/ma464/standardnormaltable.pdf