4. Refute the obtained estimate

Having access to multiple refutation methods to validate an effect estimate from a causal estimator is a key benefit of using DoWhy.

4.1. Supported refutation methods

• Add Random Common Cause: Does the estimation method change its estimate after we add an independent random variable as a common cause to the dataset? (Hint: It should not)

• Placebo Treatment: What happens to the estimated causal effect when we replace the true treatment variable with an independent random variable? (Hint: the effect should go to zero)

• Dummy Outcome: What happens to the estimated causal effect when we replace the true outcome variable with an independent random variable? (Hint: The effect should go to zero)

• Simulated Outcome: What happens to the estimated causal effect when we replace the dataset with a simulated dataset based on a known data-generating process closest to the given dataset? (Hint: It should match the effect parameter from the data-generating process)

• Add Unobserved Common Causes: How sensitive is the effect estimate when we add an additional common cause (confounder) to the dataset that is correlated with the treatment and the outcome? (Hint: It should not be too sensitive)

• Data Subsets Validation: Does the estimated effect change significantly when we replace the given dataset with a randomly selected subset? (Hint: It should not)

• Bootstrap Validation: Does the estimated effect change significantly when we replace the given dataset with bootstrapped samples from the same dataset? (Hint: It should not)

Examples of using refutation methods are in the Refutations notebook. For an advanced refutation that uses a simulated dataset based on user-provided or learnt data-generating processes, check out the Dummy Outcome Refuter notebook. As a practical example, this notebook shows an application of refutation methods on evaluating effect estimators for the Infant Health and Development Program (IHDP) and Lalonde datasets.