Unfair comparison

Dissimilar expectations

Be careful with intervention comparisons where people knew which treatment they received, and knowing that could have changed how they felt or behaved.

People who are given an intervention may feel better because they believe they are getting a superior therapy package and expect that will make them feel better. This can happen even if the intervention isn’t actually better than the comparison. It is called a “placebo effect”.

Knowing which intervention they got and having expectations about it can also change the way people behave. For example, someone who is told a specific intervention will be beneficial for their word finding difficulties may also start practising more. They may make improvements with their word finding because of the increased practise and not just because of the specific intervention they received.

One way of keeping this from happening is not to let the people who receive the treatments know which intervention they are receiving (to “blind” them).

REMEMBER: Think about whether the people in the comparison groups knew which intervention they received and, if so, whether that may have changed how they felt or behaved.