Intention-to-Treat (ITT) Instrumentation
RCTJournal Article
In field experiments, non-compliance—such as administrative failures where assigned schools fail to receive tutors or participants decline intervention—biases direct treatment estimates.
Picture this
When some assigned groups fail to receive a promised intervention, using initial random assignment as an indicator to adjust overall outcomes is like measuring a fitness program's impact based on everyone invited, then mathematically adjusting for those who actually attended the gym.
What the evidence says
In Year 2 in Mumbai, 33% of schools assigned to receive a balsakhi tutor did not receive one due to administrative difficulties; 2SLS instrumentation successfully eliminated non-compliance bias to yield unbiased direct treatment estimates.
- Who was studied
- N = 9,986 Grade 3 and Grade 4 students across 77 municipal primary schools in Mumbai, India.
- How
- Instrumental Variables (IV) / Two-Stage Least Squares (2SLS) regressing test score improvements on actual treatment status using random assignment intention-to-treat (ITT) as an instrument.
What to do
Use initial random assignment as an instrumental variable in Two-Stage Least Squares regression when evaluating educational interventions affected by program non-compliance or implementation failure.
From the source
"Throughout the paper, the schools that were assigned balsakhis but did not get them are included in the 'intention to treat' group. The regression analysis then adjusts the estimates for the fraction of the treatment group that was effectively treated by using the initial assignment as an instrument for treatment."
Remedying Education: Evidence from Two Randomized Experiments in India