## Should I use fixed or random effects meta-analysis?

Fixed-effects model should be used only if it reasonable to assume that all studies shares the same, one common effect. If it is not reasonable to assume that there is one common effect size, then the random-effects model should be used.

### What is the difference between random and fixed effects meta-analysis models?

Under the fixed-effect model there is only one true effect. Under the random-effects model there is a distribution of true effects. The summary effect is an estimate of that distribution’s mean. One of the most important goals of a meta-analysis is to determine how the effect size varies across studies.

**Should I use random effects or fixed effects?**

Under certain conditions, random effects models can introduce bias, but reduce the variance of estimates of coefficients of interest. Fixed-effects estimates will be unbiased, but may be subject to high sample dependence.

**What is a random effect meta-analysis?**

Random-effects meta-analysis is the statistical synthesis of trials that examine the same or similar research question under the assumption that the underlying true effects differ across trials.

## What is difference between random and fixed effects?

The fixed effects are the coefficients (intercept, slope) as we usually think about the. The random effects are the variances of the intercepts or slopes across groups.

### What are fixed and random effects?

**What is fixed effect model in meta-analysis?**

There are two popular statistical models for meta-analysis, the fixed-effect model and the random-effects model. Under the fixed-effect model we assume that there is one true effect size that underlies all the studies in the analysis, and that all differences in observed effects are due to sampling error.

**Why we use fixed effects?**

By including fixed effects (group dummies), you are controlling for the average differences across cities in any observable or unobservable predictors, such as differences in quality, sophistication, etc. The fixed effect coefficients soak up all the across-group action.

## What is a random-effects meta-analysis model?

A random-effects meta-analysis model assumes the observed estimates of treatment effect can vary across studies because of real differences in the treatment effect in each study as well as sampling variability (chance).

### What is a fixed-effects meta-analysis?

In a fixed-effects meta-analysis, we assume that each of the studies included are estimating the same underlying parameter .

**Is the fixed-effects approach more unbiased than random effects?**

The first thing to notice is that the fixed-effects approach is still unbiased, even though the data are being simulated based on a random-effects model. However, we see that the SD is much larger for the fixed-effects approach (0.049 vs 0.024 for the random-effects).

**How does the choice of method affect the interpretation of meta-analyses?**

Meta-analyses use either a fixed effect or a random effects statistical model. A fixed effect meta-analysis assumes all studies are estimating the same (fixed) treatment effect, whereas a random effects meta-analysis allows for differences in the treatment effect from study to study. This choice of method affects the interpretation