Post on 20-Jan-2016
Step 2: Make a Causal Model
Step 2: Make a Causal Model
Farrokh Alemi Ph.D.
This research was funded by Grant RO1 HL 084767 from the National Heart Blood and Lung
Institute.
Step 2: Make a Causal Model
Step 2: Make a Causal Model
This lecture continues from the lecture on making a list of
causes
• Real world relationships• Visual network of causes & effects• Probability distribution
Step 2: Make a Model from Your List
Put Each Cause in a Node
Put the Effect to the Right
Connect Causes to Effect
Put in Constraints
Equivalent Probability Model
Each Node a Function of Nodes Linking to It
Combination of Multiple Causes
p(Exercise | Ready to bike, Ready to shower at gym, Sleep early)= highp(Exercise | Ready to bike, Ready to shower at gym, Slept late)= Between low and high p(Exercise | Ready to bike, No plans to shower at gym, Sleep early)= Between low and high p(Exercise | No plans to bike, Ready to shower at gym, Sleep early)= Between low and high p(Exercise | Ready to bike, No plans to shower at gym, Slept late)= Between low and high p(Exercise | No plans to bike, Ready to shower at gym, Slept late)= Between low and high p(Exercise | No plans to bike, No plans to shower at gym, Slept late)= Low
Out of Sight, Out of Mind
Breakfast time
Probabilistic Dependence
Probabilistic Dependence
biking)Plan |Exercise(Exercise)( pp
Probabilistic Dependence
Probabilistic Dependence
shower) gymPlan |Exercise(Exercise)( pp
Probabilistic Dependence
early) Sleeping|Exercise(Exercise)( pp
• If we knew …• P(A|B) = P(A)
Probabilistic Independence
early) Sleeping|Exercise(Exercise)( pp
Probabilistic Independence
early) Sleeping|shower Plan to(shower) Plan to( pp
Serial Nodes: Root Causes
Rain) bike, Ready to|Exercise(
bike) Ready to|Exercise(
p
p
Multiple Causes
early) Sleeping Exercise,|shower Plan to(
Exercise)|shower Plan to(
p
p
Causa
l model
Probability distribution
Test against data
Probabilities Can Be Tested Against Data
Lecture ContinuesLecture Continues
Step 3: Thought Experiments