# Defining Causality

STAT 20: Introduction to Probability and Statistics

# Agenda

• Announcements
• Concept Questions
• Lab: A Matter of Taste

# Announcements

• Lab 7 released today, due next Tuesday
• 2 problem sets next week, due the Tuesday of R&R week

# Concept Questions

Suppose that a prisoner is about to be executed by a firing squad. A certain chain of events must occur for this to happen. First, the judge orders the execution. The order goes to a captain, who signals the two soldiers of the firing squad (soldier 1 and soldier 2) to fire. They are obedient and expert marksmen, so they only fire on command, and if either one of them shoots, the prisoner dies.

Using the conditional counterfactual definition, who caused the death of the prisoner?

A. The judge
B. The captain
C. Soldier 1
D. Soldier 2

02:00

All of the four people in the table below need to travel from Berkeley to San Francisco today, and are trying to decide whether to take BART or to drive. The table below shows travel times for each individual (assume these are the true, unknown numbers, not just predictions).

Name Travel time by car (min) Travel time by BART (min)
Maria 35 28
Fan 30 32
Alice 40 55

Pick the correct way to fill in the following sentence: “Taking BART instead of driving will cause ___ to arrive more than ___ minutes later.”

01:00

All of the four people in the table below need to travel from Berkeley to San Francisco today, and are trying to decide whether to take BART or to drive. The table below shows travel times for each individual (assume these are the true, unknown numbers, not just predictions).

Name Travel time by car (min) Travel time by BART (min)
Maria 35 28
Fan 30 32
Alice 40 55

What is the average treatment effect of taking BART on travel time for these four subjects?

01:00

All of the four people in the table below need to travel from Berkeley to San Francisco today. The table below shows the actual travel times for each individual using the method they chose to use.

Name Travel time by car (min) Travel time by BART (min)
Maria ? 28
Fan ? 32
Alice 40 ?

What is a natural estimate of the average effect of taking BART (rather than driving) if we only observed this data?

01:00

All of the four people in the table below need to travel from Berkeley to San Francisco today. The table below shows the actual travel times for each individual using the method they chose to use.

Name Travel time by car (min) Travel time by BART (min)
Maria ? 28
Fan ? 32
Alice 40 ?
03:00
05:00