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Evidence Products include Evidence Briefs, Research and Development Briefs, Evidence Summaries and potentially other forms as well. They provide systematic reviews of justice related interventions. These products will support decision-making for investing in evidence-based policy and practice to improve the lives of the New Zealand public.
The Ministry of Justice Evidence Briefs summarise New Zealand and international research, the provision of current services, and tell us how well an intervention reduces crime. Evidence Briefs can put a numerical value on effectiveness and therefore demonstrate if the intervention worked, and for whom.
Evidence Products are designed to support investment and decision making in the justice sector. The suite of Evidence Briefs, developed by the Ministry of Justice, is a ‘first-stop-shop’ for decision makers and policy developers looking to influence justice outcomes.
To make good decisions on where the government invests, we need good evidence to understand: what is effective; for whom; when; and why.
The evidence to guide decision-makers can be mixed, depending on the robustness of research into an intervention. Evidence Products summarise this evidence in a way that decision makers and policy developers can use. This includes interventions that range from strong, high quality evidence bases to evidence that is inconclusive, or evidence that supports ending an intervention.
The suite can then support
Evidence products can also assess some socio-economic outcomes beyond reoffending.
Each Evidence Brief provides a rating based on the same criteria. The final rating is built around two separate assessments, one reflecting international evidence, and another – New Zealand evidence.
Effective programmes in one country often, but not always, work in other countries. Even if international research shows that an investment type can reduce offending, it may not be worth adopting unless we are able to replicate the results in New Zealand’s crime environment.
Both international and New Zealand evidence is assessed using the Maryland Scale[1] of Scientific Methods. This is, a 5-point scale with randomised controlled trials at the top (level 5) of the scale. At lower levels, there is an increasing risk that findings are subject to selection bias with a range of challenges to their validity. Level 3 is considered to be the minimum to conclude that the intervention reduces crime.
[1] Sherman, L., Farrington, D., Welsh, B., & Mackenzie, D. (Eds). (2002). Evidence-Based Crime Prevention. New York: Routledge
Level 5 | Randomised, controlled trials |
Level 4 | Quasi-experimental design |
Level 3 | Comparison of outcomes in treated group after an intervention, with outcomes in the treated group before the intervention, and a comparison group used to provide a counterfactual (e.g. difference in difference). |
Level 2 | Use of adequate control variables and either (a) a cross-sectional comparison of treated groups with untreated groups, or (b) a before-and-after comparison of treated group, without an untreated comparison group. |
Level 1 | Before and after studies with no comparison group |
The final rating is measured in a six-grade scale varying from one for a “harmful” outcome category to six for a “strong” outcome category.
New Zealand studies | ||||||
---|---|---|---|---|---|---|
At least one level 4 or 5 study finds a statistically significant negative impact, no conflicting L4+ studies | Studies show conflicting results, or no impact | At least one level 3 study finds a statistically significant positive impact, no conflicting L3+ studies | At least one level 4 study finds a statistically significant positive impact, no conflicting L4+ studies | At least one level 5 study find a statistically significant positive impact, no conflicting L5 studies | ||
International studies | Meta-analysis/systematic review of 5+ studies finds a statistically significant positive impact, no conflicts | Fair | Promising | Strong | Strong | Strong |
MA/SR with fewer than 5 studies finds positive impact | Inconclusive | Fair | Fair | Promising | Strong | |
MA/SR find conflicting results | Inconclusive | Inconclusive | Fair | Promising | Strong | |
MA/SR shows no effect | Harmful | Poor | Promising | Promising | Strong | |
MA/SR shows negative impact, no conflicting results | Harmful | Poor | Inconclusive | Fair | Promising |
There is also a standard interpretation for each evidence rating, as summarised in the following table.
Outcome category |
Interpretation |
Strong |
|
Promising |
|
Fair |
|
Inconclusive |
|
Poor |
|
Harmful |
|
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