How is the 5+ GCSE A*-C grades indicator calculated?
The GCSE indicators are derived from an analysis of the relationship between CAT tests at age 11 and GCSE examinations at age 16 for large and nationally representative samples of pupils . An example of the actual data is shown below. Figure 1 shows the proportion of pupils achieving 5+A*-C grades for each mean CAT score. We can see that the higher the mean CAT score the greater the proportion of pupils who achieve five or more A* to C grades. For example only just over 10% of pupils with a mean CAT score of 85 achieve 5+ A*-C grades; in contrast about 95% of pupils with a mean CAT score of 115 achieve 5+ A*-C grades. Figure 1 We can use a statistical technique known as ordered logistic regression to smooth and more precisely chart the relationship between mean CAT score and proportion of pupils with 5+ A*-C grades. The result of this analysis is shown in Figure 2. It shows the probability that a pupil will achieve 5+A*-C grades, given a particular CAT score. For each pupil we can ther
