When counselors and psychologists report test scores, they often report one of the scores found in the table below. When several tests are used, it is helpful to know how the scores compare from one test to another.
A good place to begin is to locate the average score-- that's the row where z = 0. Then look at the broad middle range between z = -1 and z = 1. About 68% of people score between z = -1 and z = 1.
Intelligence Tests use Standard Scores abbreviated as SS. These scores take the place of the old IQ score. An average IQ is 100 -- about 68% of people score between 85 and 115.
Each row contains the equivalent score on a different
scoring system. For example, a z-score
of 1 equals a T score of 60, and a
standard score of 115. The score is at the 84th percentile.
|
z
|
T
|
Standard
|
Percentile
Rank
|
|
3
|
80
|
145
|
99.9
|
|
2.5
|
75
|
138
|
99.4
|
|
2
|
70
|
130
|
97.7
|
|
1.5
|
65
|
123
|
93.3
|
|
1
|
60
|
115
|
84.1
|
|
.5
|
55
|
108
|
69.2
|
|
0
|
50
|
100
|
50.0
|
|
-.5
|
45
|
93
|
30.8
|
|
-1
|
40
|
85
|
15.9
|
|
-1.5
|
35
|
78
|
6.7
|
|
-2
|
30
|
70
|
2.3
|
|
-2.5
|
25
|
63
|
0.6
|
|
-3
|
20
|
55
|
0.1
|
Table Notes
z-scores, M = 0, SD = 1
T-scores, M = 50, SD = 10
SS-Standard Scores, M
= 100, SD = 15
PR- Percentile Rank
