Impact evaluation
Last week (27 July) the Justice Data Lab published its impact evaluation of the
prison-based Thinking Skills Programme (TSP) on reoffending. Authored by Aimee Brinn, John Preston, Rosina Costello, Tyler Opoku, Emily Sampson, Ian Elliott and Annie Sorbie, the 92-page evaluation does conclude that :
“over a two-year period from release, those who had participated in TSP were less likely to reoffend, reoffended less frequently, and took longer to reoffend, compared to males who did not participate in TSP. These results were statistically significant with mostly very small effect sizes.”
About the Thinking Skills programme
The Thinking Skills Programme (TSP) is an accredited offending behaviour programme designed and delivered by His Majesty’s Prison and Probation Service (HMPPS). TSP is suitable for adult men and women assessed to be at medium and above risk of reoffending. TSP is the highest volume accredited programme delivered in custody.
The TSP is designed to reduce general reoffending by supporting improvements in four ways:
- Developing thinking skills (such as problem solving, flexible thinking, consequential thinking, critical reasoning)
- Applying these skills to managing personal risk factors
- Applying thinking skills to developing personally relevant protective factors
- Applying thinking skills to setting pro-social goals that support relapse prevention.
The programme format comprises 19 sessions (15 group sessions and 4 individual sessions, resulting in around 38 hours of contact time (dose).
The evaluation
The evaluation assessed the impact of TSP delivered in prison on proven general reoffending within a two-year follow-up period.
The analysis involved a treatment group of 20,293 adults (18,555 males, 1,738 females) who participated in the TSP programme between 2010 and 2019 and this was compared to a matched comparison group of 375,647 adults (345,084 males, 30,563 females) who did not participate in the programme. Propensity score matching (PSM) was used to ensure comparable treatment and comparison groups.
The evaluation used the largest number of PSM matching variables for a HMPPS accredited programme evaluation to date. The evaluation also has a large sample size which means it is likely to be representative of the population of TSP participants. A larger sample generates more precise results and increases the power of statistical testing. This increases the likelihood of finding a statistically significant finding (i.e., not due to chance) even if the difference between the treatment group and the matched comparison group is small.
All adults in this study were released from prison between 2010 and 2020.
Findings
The headline evaluation findings are separated by gender. (the findings from the male study are summarised in the infographic I have reproduced above). The results for both men and women were positive, although they were more positive for men. More details are provided below.
Headline results – Male
Results show that, over a two-year period from release, those who had participated in TSP were less likely to reoffend, reoffended less frequently, and took longer to reoffend, compared to males who did not participate in TSP. These results were statistically significant with mostly very small effect sizes.
Key sub-analyses – Male
The results showed that males who participated in TSP and met any of the following conditions; (a) ideally suitable for TSP, (b) completed TSP, (c) participated in TSP in a prison between 2016 and 2019 where programme integrity was broadly maintained, or (d), were at medium and above risk of reoffending (OGRS3 risk score between 50 and 100), were less likely to reoffend, reoffended less frequently, and took longer to reoffend over a two year period, compared to similar males who did not participate in TSP. These results were statistically significant with mostly very small effect sizes.
Headline Results – Female
Results showed that, over a two-year period from release, those who participated in TSP reoffended less frequently, compared to those who did not participate in the programme. These results were statistically significant and have mostly very small effect sizes.
Participation in TSP did not have a statistically significant effect on the two-year binary reoffending rate for females, or the amount of time before a female offender committed their first proven reoffence.
Key sub-analyses – Female
Female sub-analyses were limited due to small sample sizes and therefore would be less likely to produce statistically reliable results. Of those conducted, results showed that female participants of TSP who were ideally suitable for the intervention were less likely to reoffend and reoffended less frequently over a two-year follow up period, compared to females who did not participate in TSP. These results were statistically significant and have mostly very small effect sizes. There was no statistically significant effect on the time taken to reoffend for this subgroup.
Females who completed TSP reoffended less frequently within a two-year period, compared to females who did not participate in TSP. These results were statistically significant. There was no statistically significant effect on the binary reoffending rate or time taken to reoffend for this subgroup.
Conclusion
These are welcome positive results, but the analysis makes it clear that for maximum impact, people have to be suitable for the programme, they need to complete it and it needs to be delivered to the requisite high standards.
Thanks to Jose Aljovin for kind permission to use the header image in this post which was previously published on Unsplash.
