[jfz]

This is critical - even if no individual study has positive results, the data from each study can be aggregated and that meta-analysis can find results much more easily. I remember reading (but can't find the link to) an article about a medicine that took many trials to have one trial with statistical significance, but a meta-analysis of the first five or so trials would have revealed the efficacy of the drug under test much sooner and at a much lower cost.

[tmalsburg2]

Meta-analyses suffer from publication bias, though. Studies with one outcome are more likely to be published than those with some other outcome, and therefore the input for the meta-anslysis is biased.