library("causatr")
fit <- causat(nhefs, outcome = "wt82_71", treatment = "qsmk",
confounders = ~ sex + age + wt71)
contrast(fit, interventions = list(
double_odds = ipsi(2),
half_odds = ipsi(0.5)
))Incremental propensity score intervention
Description
Creates an incremental propensity score intervention (IPSI) that multiplies each individual’s odds of treatment by delta. Values of delta > 1 increase the probability of treatment; delta < 1 decrease it. This is a stochastic modified treatment policy indexed by a single scalar, and corresponds to the "shift-the-odds" counterfactual studied by Kennedy (2019).
IPSI is binary-only and is only meaningful under estimator = “ipw” – the IPW engine computes the Kennedy closed-form weight \(w_i = (\delta A_i + (1 - A_i)) / (\delta p_i + (1 - p_i))\) directly from the fitted propensity, with no counterfactual treatment value to predict at. estimator = “gcomp” and estimator = “matching” therefore do not support ipsi().
Usage
ipsi(delta)
Arguments
delta
|
Positive numeric. The odds multiplier. |
Value
A causatr_intervention object.
References
Kennedy EH (2019). Nonparametric causal effects based on incremental propensity score interventions. Journal of the American Statistical Association 114:645-656.
See Also
static(), shift(), dynamic(), scale_by(), threshold()