Doubly-Definitive Test

When to use Doubly-Definitive Test

Use this test when you need to make a definitive statement about the causal relationship between an intervention and an outcome. It provides the strongest possible support for a causal explanation.

What it solves

Need for absolute certainty about the causal relationship, desire to eliminate all alternative explanations, high stakes decision-making.

How to run Doubly-Definitive Test, step by step

1. Identify potential causal factors that could have contributed to the outcome. (10 minutes)
2. Gather evidence that would both confirm a particular causal explanation and rule out other explanations. (15 minutes)
3. Assess whether the evidence meets the criteria for a 'doubly-definitive' test. (10 minutes)
4. Document the rationale for classifying each factor as having or not having 'doubly-definitive' evidence. (5 minutes)

Materials needed

• Whiteboard or flip chart
• Markers
• Sticky notes
• Relevant documents and data

Facilitator tips

• Recognize that 'doubly-definitive' evidence is rare and may not be available.
• Be extremely rigorous in assessing the evidence and avoid overinterpreting weak evidence.
• Be prepared to acknowledge the limitations of the evidence, even if it is strong.

Common pitfalls

• Setting unrealistic expectations: Expecting to find 'doubly-definitive' evidence when it is unlikely to exist. Mitigate by acknowledging the rarity of this type of evidence.
• Overinterpreting weak evidence: Classifying factors as having 'doubly-definitive' evidence when the evidence is not strong enough. Mitigate by being extremely rigorous in assessing the evidence.

Variations

• Focus on gathering evidence that strongly supports the causal explanation and weakens alternative explanations, even if it doesn't completely rule them out.
• Use a Bayesian approach to quantify the strength of the evidence for and against different causal explanations.

Running it online or hybrid

Requires high-bandwidth communication and careful documentation of evidence. May be challenging to achieve consensus remotely.

What it produces

A report summarizing the evidence that both confirms the causal explanation and rules out alternative explanations.

Origin

Adapted from BetterEvaluation.org — source

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