Data simply refers to information about or details from a study including its methods and design, participants, setting, interventions, results, etc. Ideally, two researchers should independently extract data from each study in order to minimize errors and reduce the potential for bias. As a minimum, one researcher should extract data with a second person checking for accuracy. There should be a process in place to resolve any conflicts, like a tiebreaker.
To standardize the process and improve the validity of the results, time and thought should be given to creating a data extraction form. These can be created using general word processing software or spreadsheets.
It is important to collect enough information, during this process, to sufficiently assess each study. Collecting too much or too little information may be a waste of time and result in the omission of crucial data.