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Standardised Scores (SS) Explained


What is the difference between “raw score”, “percentage score” and “standardised score”?


Let’s take an example. 
A test has 50 questions. 
The mean(average) score for the test is 30
Let's assume 95% of pupils who sat the test scored between 20 and 40.

3 pupils; A, B and C got 20, 30 and 40 respectively in the test. 

Raw Scores:
A 20
B 30
C 40

Percentage Scores:
A 40%
B 60%
C 80%

Standardised Scores:
A 70
B 100
C 130

Standardised scores above 130 and below 70 are rare. 

So the number of correct answers is the raw score, the raw score as a fraction of the total possible multiplied by 100 is the percentage score

The standardised score can range approximately from 50 up to 150, 50% of pupils will be lower than 100 and likewise, 50% will be above 100.

This is roughly how they are split up:
2.5% are lower than 70
13.5% are between 70 and 85
14% are between 85 and 92
20% are between 92 and 100
20% are between 100 and 108
14% are between 108 and 115
13.5% are between 115 and 130
2.5% are greater than 130

BOFA shows standardised scores for all tests, each score is recalculated every night and takes into account all the new tests which have been completed during the day. Every test has a different average(mean) and different spread of the data(standard deviation), this means you can compare scores across multiple tests, some tests may be easier than others , but generally speaking, all tests at the same level in any particular topic should in theory be similar.