which type of research studies are considered classic or classic? how often do you need to do a retrospective study what type of study is a retrospective study what are some examples of retrospective studies retrospective study definition retrospective studies examples why are retrospective studies considered logical what is the purpose of retrospective study? when did the risk factor analysis of retained surgical instruments begin what is a retrospective study why is retrospective study considered a classic which is an example of a retrospective study what type of studies can i look at for risk factors what kind of studies are in general surgery what type of research is retrospective study what kind of data are retrospective studies which is an example of retrospective studies who is involved in the risk factor study? which clinical journals use statistical methods to analyze risk factors of retained instruments? which type of study is an example of a textbook study?