The EEF’s months of additional progress measure

For EEF trials, the Months’ Progress measure shows the number of additional months of progress that children and young people receiving the intervention made, on average, compared to the 'control group' of children and young people who did not receive it.

You should always consider the EEF ‘padlocks’ security rating as well as the Months’ Progress measure. For some projects, the Months’ Progress is high, but the security rating shows that we have limited confidence in the finding. For more information about the EEF ‘padlocks’ security rating see here.

The measure is based on the ‘effect size’ of the intervention, which is calculated by the independent evaluator. The effect size describes the size of the difference between two groups in a standard and comparable way. However, it can be difficult to understand what a given effect size will mean for the progress of children and young people. That is why the the EEF translates effect sizes into a measures of months of additional progress, as shown in the table below.

Effect size fromtoMonths' additional progress

Effect sizes presented to the nearest 2 decimal places.

For negative effect sizes, the conversion from effect size to months of additional progress is of the same size as shown in the table but negative in value.

If the months' progress figure is negative, this does not necessarily mean that children and young people have made negative progress. It means that they have made less progress than the control group of children and young people.

Note that the conversion from effect size to additional months' progress differs slightly between the reports for individual EEF-funded projects, as described above, and the EEF Teaching and Learning Toolkit. For more information on the conversion for the Toolkit see here