Hi Colleagues,
Please advise on models or procedures (literature) I can consult for using a matching procedure to assign participants to a treatment and control group in a quasi-experiment. I'm aware that due to non-randomization, selection bias is a major threat to the internal validity of my research. Therefore, I wish to control for any biases of covariates in the design and data analysis. I've come across pair matching, stratification, and covariate adjustment but have found no practical procedure as to how I can propose to implement these models in my study. I know that matching participants to a control and treatment group, one must ensure that participants have a great deal of 'similarity' to reduce the non-equivalence.
So, simply put: Do you know of any practical models that i can use in my research to do matching or participants in a quasi-experiment?
Check prospensity score matching ( modeling the group assingnment using pre interventional covariates).
This is a great introduction:
http://www.ipr.northwestern.edu/workshops/past-workshops/quasi-experimental-design-and-analysis-in-education/recent-articles/docs/QE2010-MatchingPS.pdf
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3144483/
Hope that helps, best wishes, Manuel
Dear Booysen,
Essentially, when we create two or more groups in a study, we aim to make the groups similar in almost all aspects except in relation to what we intend to study - that we would not yet be aware of. This means that before matching participants, the researcher must know the characteristics of his/her study population so that subjects with similar features are assigned to both control and experimental groups. The easiest way to do this is first to group your subjects into homogeneous groups; then later assign members of the homogeneous stratum to the different groups so that the two groups are somehow similar. This means that the difference that will eventually emerge after the intervention you will cause will most certainly arise from that intervention. I am not sure whether I am clear on this?
David
Dear David & Manuel,
Thank you for the input. What you have said regarding the similarities and propensity score matching have come up a lot from other sources that I have consulted. Thanks again and keep well.
Duane
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