Fixed Effects Model: Answers the question whether the studies included in the meta-analysis show that the treatment or exposure produced the effect on average

Random Effects Model: Answers the question, on the basis of the studies that are examined, is it possible to comment that the treatment or the exposure will produce a result?

A random effects model is computationally more intense than a fixed effects model. Also, if the studies are homogeneous, fixed effects and random effects models are similar.

In this tutorial, we will also examine special situations when the outcomes are on a continuous scale, rather than discrete counting of events.

Finally, check out this table about the methods to be used for different types of models.