Assessment & Blinding

If the member of staff who is doing the assessment knows whether pupils are in the intervention or control group bias can creep in. This is not about cheating or lying – the bias is subconscious and inevitable however honest we think we are being. There are two main ways to address this:

This may seem like a lot of trouble to go to and in some cases may not be possible. However, there is a lot of evidence that un-blinded judgement-based assessments are biased, often substantially so.