intro for causality · 2020-05-06 · causal inference for statistics, social, and biomedical...
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Intro for CausalityDinghuai Zhang 2020.4
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Two branches
• Donald Rubin• potential outcome• goal: causal effect
• bio-stats & bio-medical
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Two branches
• Judea Pearl• Directed Acyclic Graph (DAG) • causal discovery• stats & ml
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• Bernhard Schölkopf
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Confounder
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Structral Causal Model (SCM)
•A → T
• independence of cause and mechanism:• N_A N_T• p(a,t) = p(a)p(t|a)
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connection with SSL
• Semi-supervised learning used unlabeled X to help• if and are indeed independent, • then SSL won’t help
• therefore, all cases where SSL helps is anti-causal
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p(a,t) = p(a)p(t|a) or p(t)p(a|t) ?
• IF • intervening on A has changed T , but intervening on T has not
changed A • THEN • we think A → T
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Intervention
• C → E (cause → effect)
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Counterfactual
• T = 1: with treatment• N_B = 0: normal patient N_B = 1: rare patient• B = 0: healthy B = 1: blind
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Simpson’s paradox
conditional prob compare:
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• Z: size of the stone• R: whether recovery
• instead of compare conditional probability• we should compare intervention probability:
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If equal, then X -> Y
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Learning Cause-Effect
• Identifiability• additional assumptions are required
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Structure Identification
• Given (X, Y) ~ dataset
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Alternative approach
• compare independence:• p(x) p(y|x) or p(y) p(x|y) ?
Supervised learning approach
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Thank you for listening