Standardisation
3.2 Standardising raw examination marks to ensure fairness
Each year, examiners aim to set papers for a course (at Stage 2 and Stage 3) that have an average raw examination mark of about 60, with only the most outstanding students scoring in the high 90s or 100. Generally, the examiners succeed in this aim, but until the students sit the examination and it is marked, the actual average and marks spread will be unknown.
Standardisation is a process which takes care of a situation where the distribution of examination marks is not as required. Standardisation takes account of differences in the difficulty of examinations from year to year and ensures that students are not disadvantaged if an examination is harder than usual in a particular year.
If the examination is harder than usual, the standardised examination marks in that unit pair may be higher then the raw marks. If, on the other hand, the examination is easier than usual, the standardised examination marks may be lower than the raw examination marks.
All raw examination marks for a stage are standardised. This means that they are brought onto a common scale which has a mean (average) of 60 and a standard deviation (spread) of approximately 15. This distribution of marks is represented in Figure 1.
3.3 Standardisation procedure
Figure 2 shows how the raw examination marks at a stage are standardised to achieve the distribution shown in figure 1.
The top 2% of raw examination marks are adjusted to fit into the standardised mark range of 90 to100 marks, with the top raw examination mark being awarded 100 standardised examination marks.
The next lowest 6% of raw examination marks are adjusted to fit in the range of 80 to 90 standardised marks.
The next lowest 15.1% of raw examination marks are adjusted to fit in the range of 70 to 80 standardised marks.
At the bottom end of the scale, a raw examination mark of zero will be given a raw standardised mark of zero, and the lowest 0.2% of raw examination marks are adjusted to fit into the range of zero to 10 standardised marks.
3.4 The effect of Standardisation
The effect of standardisation can be shown in pictorial form. Five cases are shown below.
Case 1
The examination marks have the same spread (standard deviation of 13 marks) as the standardised distribution, but the average raw examination mark is greater than that of the standardised distribution: the standardised examination marks generally will be less than the raw examination marks.
Case 2
The examination marks have the same spread (standard deviation of 13 marks) as the standardised distribution, but the average raw examination mark is less than that of the standardised distribution - this means that the standardised examination marks generally will be greater than the raw examination marks.
Case 3
The examination marks have the same average (60 marks) as the standardised distribution, but the spread (standard deviation) of the raw examination marks is less than that of the standardised distribution - this means that the standardised marks will be more spread out than the raw examination marks. As a consequence, for candidates in the top half of the distribution, standardised examination marks generally will be greater than the raw examination marks, but for candidates in the lower half of the distribution, the standardised examination marks generally will be less than the raw examination marks.
Case 4
The examination marks have the same average (60 marks) as the standardised distribution, but the spread (standard deviation) of the raw examination marks is greater than that of the standardised distribution - this means that the standardised marks will be less spread out than the raw examination marks. As a consequence, for candidates in the top half of the distribution, standardised examination marks generally will be less than the raw examination marks, but for candidates in the lower half of the distribution, the standardised examination marks generally will be greater than the raw examination marks.
Case 5
The examination marks have a higher average (greater than 60 marks) than the standardised distribution, and the spread (standard deviation) of the raw examination marks is greater than that of the standardised distribution - this means that the standardised marks will be less spread out than the raw examination marks, and they generally will be less than the raw examination marks.
