Suppose we run an experiment and measure several possible independent variables after treatment. Which of the following best characterizes why this is a problem?
A) Independent variables measured after treatment may be affected by the treatment and may therefore soak up some of the treatment effect.
B) Including post-treatment variables will induce multicollinearity.
C) Post-treatment variables will not satisfy the inclusion condition.
D) Including post-treatment variables will cause imbalance in the treated and control groups.

Question

Quizplus · Accepted Answer

Independent variables measured after treatment may be affected by the treatment and may therefore soak up some of the treatment effect. Including post-treatment variables in the analysis may introduce bias and make it difficult to isolate the true effect of the treatment on the outcome variable.

Suppose We Run an Experiment and Measure Several Possible Independent