Longitudinal Research

trend studies

a longitudinal in which a topic is restudies using different groups of respondents. For example, the Roper studies of the credibility of the media.

panel studies

a research technique in which the same sample of respondents is measured at different points in time. The panelists remain the same.

cohort analysis

a study of a specifc population as it changes over time.

cohort

any group of individuals who are linked in some way or who have experienced the same significant life event within a given period.

advantages of trend studies

describes long-term changes in a population establishes patterns and can detect shifts. secondary analysis offers much possibility for trends.

disadvantages of trend studies

false trends may result from faulty data. must be based on consistent measures (e.g. consistently worded questions) constructs and operationalization may change and develop over time-making trends difficult to assess.

advantages of cohort analysis

highly flexible -less likely to have maturation; insight on maturation and socilal, political, cultural change can be less expensive than experiments or surveys original and secondary data is useful

age cohort/birth cohorts

most popular cohorts.

Pure age effect

results by age are constant over time.

pure period effect

results by period are equal over time.

disadvantages

tabular evaluations of dependent variable or criterion variable not always as clear-cut as the example in the book. variables are likely to confound each other morality

types of longitudinal studies

trend studies, cohort analysis, panel studies

pure cohort effect

cohort results are not changed by age or period.