Meta-analysis is not a hypothesis-testing activity, and cannot legitimately be used to establish the reality of a putative hazard or therapy. The proper use of meta-analysis is to increase the precision of quantitative estimates of health states in populations.

What should a meta-analysis include?

The steps of meta analysis are similar to that of a systematic review and include framing of a question, searching of literature, abstraction of data from individual studies, and framing of summary estimates and examination of publication bias.

Does a systematic review have a hypothesis?

The first BMJ book on systematic reviews went even further, noting that systematic reviews are hypothesis-testing mechanisms [15]. ... Answering such closely specified research questions remains a key role for systematic reviews.