| ||Literature Coverage Dates||Number of Studies||Number of Study Participants|
|Meta-Analysis 1||1976 - 1997||17||0|
|Meta-Analysis 2||1990 - 2005||3||0|
|Meta-Analysis 3||1980 - 2011||34||0|
Wilson, Gallagher, and MacKenzie (2000) examined the effectiveness of corrections-based education, vocation, and work programs for adult offenders through a meta-analysis of 33 experimental and quasi-experimental evaluations. Studies were included in the meta-analysis if they 1) evaluated an education, vocational, or work program for convicted adults or persons identified by the criminal justice system, 2) provided a postprogram measure of recidivism (including arrest, conviction, self-report, technical violation, or incarceration), 3) included a nonprogram comparison group (i.e., a comparison group that did not receive an educational, vocational, or work program), 4) were published after 1975 in English.
A thorough search of the literature led to the inclusion of 33 eligible studies. The program comparison–contrast was the unit of analysis, allowing for multiple program comparison–contrasts per study. The 33 studies reported 53 program comparison–contrasts that were identified and coded for the analysis. More than 40 percent of the studies (14 out of 33) were from journal articles or book chapters. The other studies were either government documents (10 out of 33) or unpublished manuscripts (9 out of 33). The studies generally had large sample sizes. The median number of participants across the program groups was 129, and the median number across the comparison groups was 320 (a total number of participants was not provided). Slightly fewer than half of the studies included only male participants. Female participants were included in 19 studies; however, they generally represented less than 21 percent of the study sample, therefore it is difficult to generalize findings from the analysis to women. In the remainder of the studies, it was unclear whether study participants included both men and women. Information on the age and racial/ethnic breakdown of the study samples was not provided.
Most of the studies (17 out of 33) examined the relative effects of vocation training. The outcome data for adult basic education and GED programs are often combined in reports. Therefore, the authors combined the few studies that examined the effects of adult basic education and GED programs separately with those studies reporting only a combined effect (11 out of 33).
The form of effect size selected was the odds ratio. Recidivism was the primary outcome of interest. This was measured as a dichotomy (i.e., the percentage or proportion of program and comparison participants who recidivated). Employment status was also an outcome of interest in the analysis; however, only 16 studies provided data on the results of employment once offenders were released to the community.Meta-Analysis 2
The 2006 meta-analysis by Aos, Miller, and Drake updated and extended an earlier 2001 review by Aos and colleagues. The overall goal of the review was to provide policymakers in Washington state with a comprehensive assessment of adult corrections programs and policies that have the ability to affect crime rates. This meta-analysis concentrated exclusively on adult corrections programs.
A comprehensive search procedure was used to identify eligible studies. Studies were eligible to be included if they 1) were published in English between 1970 and 2005, 2) were published in any format (peer-reviewed journals, government reports, or other unpublished results), 3) had a randomly assigned or well-matched comparison group, 4) had intent-to-treat groups that included both complete and program dropouts, or sufficient information was available that the combined effects could be tallied, 5) provided sufficient information to code effect sizes, and 6) had at least a 6-month follow-up period and included a measure of criminal recidivism as an outcome.
The search resulted in the inclusion of three studies of in-prison vocation education. The three studies included 1,950 adult participants in the treatment groups (no information was given on the number of control group participants). One study was published in a journal. The other two studies were government reports. No information was provided on the age, gender, or racial/ethnic breakdown of the studies’ samples, nor on the location of the programs.
The mean difference effect size was calculated for each program. Adjustments were made to the effect sizes for small sample sizes, evaluations of “non–real world” programs, and for the quality of the research design. The quality of each study was rated using the University of Maryland’s five-point scale; only studies that received a rating of 3 or higher on the scale were included in the analysis (a rating of 3 means a study used a quasi-experimental design with somewhat dissimilar treatment and comparison groups but there were reasonable controls for differences). Once effect sizes were calculated for each program effect, the individual measures were added together to produce a weighted average effect size for a program or practice area. The inverse variance weight was calculated for each program effect, and those weights were used to compute the average. The fixed-effects model was used for the analysis.Meta-Analysis 3
Davis and colleagues (2013) conducted a meta-analysis of evaluations examining the effectiveness of programs that provide education to incarcerated adults. A comprehensive literature search was done that covered the period from Jan. 1, 1980, through Dec. 31, 2011. To be included in the review, a study needed to 1) evaluate an eligible intervention, 2) measure success of the program using an eligible outcome measure, and 3) employ an eligible research design. Eligible interventions were defined as educational programs administered in jails or prisons in the United States and published (or released) during the period covered by the review. In this review, adult basic education was defined as basic skills in arithmetic, reading, writing, and, if needed, English as a second language. Adult secondary education was defined as instruction to complete high school or prepare for certificate of high school equivalency, such as the GED. Eligible outcomes were defined as measures of recidivism (including reoffending, rearrest, reconviction, reincarceration, technical parole violation, and successful completion of parole), employment (including having ever worked part time or full time since release, having been employed for a specified number of weeks since release, and employment status), and achievement test scores. Eligible research designs were those in which there is a treatment group composed of inmates who participated in and/or completed the correctional education program under consideration and a comparison group composed of inmates who did not.
The search resulted in the inclusion of 58 eligible studies. Of the 58 studies, 34 looked at the effectiveness of adult basic education on recidivism rates and 9 looked at the impact on obtaining employment. No information was provided on the age, gender, or racial/ethnic breakdown of the studies’ samples. The programs were located at correctional facilities throughout the United States.
The meta-analysis used a random-effects approach. The form of effect size selected was the odds ratio. The quality of each study was rated using the University of Maryland’s five-point scale; only studies that received a rating of 2 or higher on the scale were included in the analysis (a rating of 2 means a study used a quasi-experimental design but there were substantial baseline differences between the treatment and comparison groups that may not be controlled well for). The U.S. Department of Education’s What Works Clearinghouse (WWC) rating scheme was also used, because the WWC instrument scores education studies; however, the Maryland Scale was primarily used to determine the rigor of studies.