The common effect model

The common effect model assumes that although each study has slightly different results, they all describe the same ultimate truth, and any variations in findings between studies are just due to chance.

It’s as if you tossed a fair coin multiple times – you might not get an even number of heads and tails every time, but you’d know that the odds of getting one or the other is still always 50%.

Let’s take a look at an illustration of the common effect model.