Epidemiology 1

Pharmacoepidemiology Rahaf Alosaimi

Quasi 01 experimental design

Quasi experimental design The prefix quasi means “resembling.” Thus quasi- experimental research is research that resembles experimental research but is not true experimental research. Although the independent variable is manipulated, participants are not randomly assigned to conditions or orders of conditions because it does not involve random assignment to conditions. For these reasons, quasi-experimental research is generally higher in internal validity than correlational studies but lower than true experiments . .

Example Psychology: dr.jones is a personality expert who studies the impact the personality traits have on intelligence for purposes of her current research project She is interested in examining the IQ scores of people who score highly in each of the Big five personality factors .

types of quasi-experimental research designs: 01 02 interrupted time series design Nonequivalent Pretest Groups Design posttest design A time series is a set o measurements taken at intervals When participants are not the dependent variable randomly assigned to conditions, is measured once over a period of time however, the resulting groups before the treatment is Ex: a manufacturing company might are likely to be dissimilar in some implemented and once measure its workers’ productivity each after it is implemented ways. For this reason, week for a year. Notice that the researchers consider them to be 03 interrupted time-series design is like a nonequivalent. A nonequivalent pretest- posttest design in that it groups design, then, is a includes measurements of the between-subjects design in dependent variable both before and which participants have not after the treatment. It is unlike the pretest-posttest design, however, in that been randomly assigne to conditions it includes multiple pretes and posttest measurements . t . f . . d

Longitudinal 02 design

Longitudinal design Longitudinal studies Follow the same groups of people over long period of time, often years or decades, to see how they change Generally, they are observation in nature, with quantitative and/or qualitative data obtained on any range of exposures and effects without any external effect. .

Types of longitudinal studies: Panel study Cohort study Retrospective study Involves sampling Involves selecting a Involves looking to a cross section of group based on a the past by looking individual specific event such at historical The key feature of as birth, geographic, information such panel studies is location, or historical as medical records that they collect experience repeated measures from the same sample at different points in time.

Advantages • Effective in determining variable patterns over tim • Ensure clear focus and validity. • More powerful than cross-sectional studies • Very effective in doing research on developmental trends. • Highly flexible. • Provide high accuracy when observing changes. . e

Example

References • Cook, T. D., & Campbell, D. T. (1979). Quasi- experimentation: Design & analysis issues in field settings. Boston, MA: Houghton Mifflin • Posternak, M. A., & Miller, I. (2001). Untreated short-term course of major depression: A meta- analysis of studies using outcomes from studies using wait-list control groups. Journal of Affective Disorders, 66, 139–14 • Sforza, E., Gauthier, M., Crawford-Achour, E., Pichot, V., Maudoux, D., Barthélémy, J. C., & Roche, F. (2012). A 3-year longitudinal study of sleep disordered breathing in the elderly. The European respiratory journal, 40(3), 665–672. https://doi.org/10.1183/09031936.0013301 • Ross, K. R., Gupta, R., DeBoer, M. D., Zein, J., Phillips, B. R., Mauger, D. T., Li, C., Myers, R. E., Phipatanakul, W., Fitzpatrick, A. M., Ly, N. P., Bacharier, L. B., Jackson, D. J., Celedón, J. C., Larkin, A., Israel, E., Levy, B., Fahy, J. V., Castro, M., Bleecker, E. R., … Gaston, B. (2020). Severe asthma during childhood and adolescence: A longitudinal study. The Journal of allergy and clinical immunology, 145(1), 140–146.e9. https://doi.org/10.1016/j.jaci.2019.09.030 • Caruana, E. J., Roman, M., Hernández-Sánchez, J., & Solli, P. (2015). Longitudinal studies. Journal of thoracic disease, 7(11), E537–E540. https://doi.org/10.3978/ j.issn.2072-1439.2015.10.63 . 1 6