1. Using z-scores z-scores make it easy to compare test results.
Which was the best subject from the 3 below?
Subject
Mean
Mark
z-scores
Biology
English
Standard Deviation 62 64
Music 68 60 54 70 4 5 2
Don’t forget, these are calculated by doing
0.5 2 -1
Obviously, English was the best result (it had the biggest z-score), Biology was second best and Music was third.
Saturday, December 01, 2018Saturday, December 01, 2018
Mr M Kennedy

2. What about those 2 exam marks we looked at earlier?84
4 Marks above the mean 
Less than 1 st. dev. above the mean
5.2 59
4.0
Exactly 1 st. dev. above the mean
Exam
Mean
Circled Mark
Comment
Term 2
Trial H.S.C.
Standard Deviation 88 63
Term 2 Exam
Trial Exam
z =
z =
z =
z =
z 
0.76
z = 1
Which exam result was better, the 88 or the 63?
Despite the term 2 exam having a higher number, the trial exam mark of 63 was a better result because it has a higher z-score
Saturday, December 01, 2018Saturday, December 01, 2018
Mr M Kennedy
Time for some practice exercises!…. Worksheet 9:2