Difference between retrospective and prospective how to#
The other key concept in the retrospective study was the “cookbook,” which contained detailed instructions for how to calculate the benefits in each cell of the matrix. Even when it was impossible to quantify the benefit, as was often the case, a qualitative description of the benefits associated with a given cell still provided considerable useful information. The matrix does a good job of summarizing the complexities of programs and gives decision makers the ability to compare, although in a limited way, DOE programs according to their expected principal outcomes.Įach of the nine cells in the benefits matrix thus became an easily distinguished (and mutually exclusive) category of benefits. The “knowledge” column recognized the benefit of lessons learned from an R&D program or project that would advance our understanding of related science and technology.Īllowed programs to be compared in a way that is easily understood. Benefits that might be realized if circumstances change in the future were included in the “options benefits and costs” column. Benefits that had been realized or were expected to be realized were included in the “realized benefits and costs” column. Identified various outcomes of the R&D programs, ranging from successful deployment of a technology in private markets to the generation of knowledge that was useful but did not result in a successful technology. These were captured in the rows of the matrix. Sion makers for assessing R&D benefits because it accomplished three things:įocused attention on the public good benefits-economic, environmental, and security-that are the objective of DOE’s applied energy R&D programs. FIGURE 2-1 Matrix for assessing benefits and costs retrospectively.
related methods are risk (prospective), relative risk meta-analysis, risk difference meta-analysis and proportionsĬopyright © 2000-2019 StatsDirect Limited, all rights reserved. prone to the bias of change in methods over time. 
prone to attrition bias (compensate by using person-time methods). may uncover unanticipated associations with outcome. yields true incidence rates and relative risks. The following notes relate cohort to case-control studies: related methods are risk (retrospective), chi-square 2 by 2 test, Fisher's exact test, exact confidence interval for odds ratio, odds ratio meta-analysis and conditional logistic regression.Ĭohort studies are usually but not exclusively prospective, the opposite is true for case-control studies. controls are selected on the basis of not having the outcome. The following notes relate case-control to cohort studies: Prospective investigation is required to make precise estimates of either the incidence of an outcome or the relative risk of an outcome based on exposure.Ĭase-Control studies are usually but not exclusively retrospective, the opposite is true for cohort studies. You should take special care to avoid sources of bias and confounding in retrospective studies. In retrospective studies the odds ratio provides an estimate of relative risk. If the outcome of interest is uncommon, however, the size of prospective investigation required to estimate relative risk is often too large to be feasible. For this reason, retrospective investigations are often criticised. Most sources of error due to confounding and bias are more common in retrospective studies than in prospective studies. Many valuable case-control studies, such as Lane and Claypon's 1926 investigation of risk factors for breast cancer, were retrospective investigations. Prospective studies usually have fewer potential sources of bias and confounding than retrospective studies.Ī retrospective study looks backwards and examines exposures to suspected risk or protection factors in relation to an outcome that is established at the start of the study. All efforts should be made to avoid sources of bias such as the loss of individuals to follow up during the study. The outcome of interest should be common otherwise, the number of outcomes observed will be too small to be statistically meaningful (indistinguishable from those that may have arisen by chance). The study usually involves taking a cohort of subjects and watching them over a long period. Retrospective StudiesĪ prospective study watches for outcomes, such as the development of a disease, during the study period and relates this to other factors such as suspected risk or protection factor(s). 
Open topic with navigation Prospective vs. Prospective, Retrospective, Case-control, Cohort Studies - StatsDirect
0 kommentar(er)
