Two comparison groups were selected using the propensity-score methods
Two comparison groups were selected using the propensity-score methods to match the sixteen treatment groups. One group was obtained from SDDAP restructuring programs whereas the second group was obtained from NELS data. The propensity-score matching helped in selecting a comparison group that had average similar characteristics to those of the treatment group and not an exact match. Agodini and Dynarski (p. 185) utilized the logit model estimates to determine comparison groups, followed by assignment of a propensity score to members of treatment groups as well as the equivalent comparison member and finally selecting the nearest neighbor from the comparison group and assigning to the treatment group subject. The t-test helped determine how similar propensity scores were for the treatment and comparison subjects. Further, an f-test helped in determining how similar the characteristics of the two groups were collective. A p-value greater than.05 for both tests indicated that the two groups matched well in their characteristics. Several characteristics were used to determine the eligibility of subjects and these included demographic characteristics, parental education, time use, school attendance and participation in school activities, the student’s background as well as academic performance of students among others. To determine standard errors in the experimental impacts, the authors used standard analytic formula whereas those of propensity-score were determined using bootstrap methods.
