A student scores 61 on a test. The class average is 81, with a standard deviation of 10 points. What percentage of the class scored below this student?

Question

A student scores 61 on a test. The class average is 81, with a standard deviation of 10 points. What percentage of the class scored below this student?

 

How do I solve this problem?  Any help would be greatly appreciated.  Please and thank you!

Answer 1

Get a z-score chart:

https://www.stat.tamu.edu/~lzhou/stat302/standardnormaltable.pdf

 

z = (X - μ) / σ, where X = score, μ = mean, σ = standard deviation.

 

z = (61 - 81) / 10

z = -20 / 10

z = -2

 

2.275% scored below this student