study design

Content:

The classifications of study design used in Dr Petitti’ lecture are epidemiology, medicine and program evaluation research.


There are three types of studies for epidemiology and medicine: descriptive studies, observational studies and experimental studies. And for evaluation research are experimental and quasi-experimental.

Descriptive studies are widely used in clinical medicine and public health for description. Dr Petitti gave the famous examples of AIDS and HIV.

Prevalence and incidence are two important terms for observational studies. Time is a critical element. So there are cross-sectional study, cohort study and case-control study. Much emphasis was put on case-control study, because it is efficient. You can find cases and controls and ascertain exposure and risk factors at same time. You can find the causal inference of stroke and Migraine headache by asking the survivals of stroke, but not waiting for stroke.

Randomization will affect the outcomes of the experimental studies. Because of its limitations, quasi-experimental design is introduced. No researchers’ assignments of intervention are involved in quasi-experimental design. And other design features are substituted for randomization process. Actually, I am a little confused with time series analysis and interrupted time series analysis. I google it and find that it is widely used for data analysis. There are two main goals of time series analysis: (a) identifying the nature of the phenomenon represented by the sequence of observations, and (b) forecasting (predicting future values of the time series variable). A common research questions in time series analysis is whether an outside event affected subsequent observations. For example, did the implementation of a new economic policy improve economic performance; did a new anti-crime law affect subsequent crime rates; and so on. In general, we would like to evaluate the impact of one or more discrete events on the values in the time series. So I think interrupted time series analysis is much more like to inspect the correctness of time series analysis.

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Posted by  Xiaoxiao