A researcher conducting a retrospective study typically utilizes administrative databases, historical records, or interviews with those who have been associated with the incident. At times, if the person about whom the study is being undertaken, is already dead, then we do the interviews with persons who've been associated with him/her. In general, the reasons to conduct a retrospective study can be summarized as:
Prospective Study: In contrast, a prospective study looks ahead in the time domain. This type of study is slow as compared to the retrospective study. At times the study goes on for years together to arrive at any conclusive decision. This type of study is best suited for establishing relationships between the outcome of interest and exposure variables. The primary feature of prospective study is of course that, the outcome has not yet occurred while initiating the study and information is collected over time to assess relationships with the outcome. In such of study information is gathered mostly using interviews or observations. Two types of prospective studies are;
i. Prospective cohort studies: In this type subjects are identified beforehand and the outcome is measured over time. Here the investigator can establish a temporal relationship between a happening and an outcome, or he may follow the natural occurrences over time and then record them.
ii. Randomized controlled trials: Such types of studies are very much prevalent in undertaking medical researches. Here the subjects are randomly assigned to receive the intervention or control treatment, and outcomes are evaluated after the intervention period.
The Literary Digest used to be an influential general-interest magazine in US in the early 20th century. Published by Funk and Wagnalls, this magazine started in 1890 was later merged into Time Magazine in 1938. One of the major factors for this magazine to lose its identity was the poll conducted by this magazine about the likely outcome of the 1936 presidential elections. The poll professed that governor of Kansas Alf Landon would be the overwhelming winner. Seeing the past record of the magazine people did believe it. Moreover, it was also believed that whosoever carried Maine, will carry the nation as well. But it was not to be. The final count was very stunning for all, Running Mate's Electoral Vote for Democrat candidate, Franklin D. Roosevelt stood at 523, while it was a paltry 8 for the republican candidate Alfred Mossman Landon. Roosevelt carried 46 of the 48 states, leaving just two for his rival. This proved to be death knell for Literary Digest.
To predict the results of elections the Literary Digest