[2] This is crucial when the anticipated benefit from a treatment will be relatively small, or an expected outcome is likely to be uncommon, making a larger sample size necessary.
In studying novel pharmaceuticals, Phase III trials, which compare the new treatment to an established one, are usually multicenter ones.
[4] The benefits of multicenter trials also include the potential for a more heterogenous sample of participants, from different geographic locations and a wider range of population groups, treated from physicians of different backgrounds, and the ability to compare results among centers, all of which increase the generalizability of the study.
In many cases, efficacy will vary significantly between population groups with different genetic, environmental, and ethnic or cultural backgrounds ("demographic" factors); multicenter trials are better at evaluating these factors, by giving the opportunity for more subgroup analyses.
[4] On the other hand, a more heterogeneous study population generally requires a larger sample size to detect a given difference.