AP STATS: 50 point quizSit with your partner. This is open notes/textbook. Work for 20 minutes with your partner on the quiz. Each person will have to hand in their quiz separately though. Whatever you don’t finish today will be for tomorrow. I will collect these tomorrow. It is open notes/textbook at home as well.

Agenda• Today: Finish Chapter 4 (4.3 determining Causation)• Friday: Review Chapter 4 and Cumulative review• Monday: Drop• Tuesday: Review for cumulative Test (Chapter 1-4)• Wednesday: Cumulative Test (counts just like a regular test).• Thursday-Thanksgiving Break (Chapter 5)

With your partner…• Spend 8 minutes reading the beginning of the chapter from

Darrell Huff’s “How to Lie with Statistics”.

• We will be discussing causation and how to determine causation!

Why Causation is hard to determine?

Remember Association does NOT imply causation.

Consider this from Freakonomics:8 of the factors show a strong correlation – positive or negative – with test scores. The other 8 don’t seem to matter. Guess which one’s matter:• 1.) The child has highly educated parents• 2.) The child’s family is intact• 3.)The child’s parents have high socioeconomic status• 4.) The child’s parent’s recently moved into a better neighborhood• 5.) The child’s mother was thirty or older at the time of the first child’s birth• 6.) The child’s mother did NOT work between birth and kindergarten.• 7.)The child had low birth weight.• 8.) The child attended Head Start• 9.) The child’s parents speak English in the home.• 10.) The child’s parent’s regulalry take them to museums• 11.) The child is adopted.• 12.) The child is regularly spanked• 13.) The child’s parents are involved in the PTA.• 14.) The child frequently watches TV• 15.) The child has many books in his home.• 16.) The child’s parents read to him nearly everyday.

Consider this from Freakonomics:8 of the factors show a strong correlation – positive or negative – with test scores. The other 8 don’t seem to matter. Guess which one’s matter:1.) The child has highly educated parents2.) The child’s family is intact3.)The child’s parents have high socioeconomic status4.) The child’s parent’s recently moved into a better neighborhood5.) The child’s mother was thirty or older at the time of the first child’s birth6.) The child’s mother did NOT work between birth and kindergarten.7.)The child had low birth weight.8.) The child attended Head Start9.) The child’s parents speak English in the home.10.) The child’s parent’s regulalry take them to museums11.) The child is adopted.12.) The child is regularly spanked13.) The child’s parents are involved in the PTA.14.) The child frequently watches TV15.) The child has many books in his home.16.) The child’s parents read to him nearly everyday.

Look at the following relationships.

Establishing CausationCausation (Amount of Sugar Consumed Vs. Cavities)

Common Response (lurking variable): (Firefighters at a fire versus property damage)• Association is due to a common response to the lurking variable.• Might be no direct association between x and y.

Confounding: Years in school vs. Salary or Healthy Diet vs. Life Span

Confounding lurking variables.

The diet is confounded by other variables like exercise, wealth, etc.

Confounding Variables

• Two variables are confounded when their effects on the response variable cannot be distinguished from each other.

• In other words, BOTH the explanatory variable AND the lurking variable may influence the response variable y. Because they are confounded we can NOT distinguish the influence of x from the influence of z.

THE BIG IDEA• Even a very strong association between two variables is NOT

by itself good evidence that there is a cause and effect relationship between two variables.

• SO HOW DO YOU ESTABLISH CAUSATION????

• THE BEST WAY IS TO CONDUCT A CAREFULLY DESIGNED EXPERIMENT (that way you can control for the lurking variables).

The Problem…• Many disputes can NOT be settled with an an experiment

(oftentimes because of ethical or practical reasons).

• Does gun control reduce violent crime? Does living near a power line CAUSE cancer? Has increased free trade helped to increase the gap between the incomes of more educated and less educated American workers?

Solution: How to establish causation when you can’t do an experiment!

• For example: How could you help to PROVE that smoking causes lung cancer without an experiment?

Criteria for Establishing Causation (without an experiment)

Brain Break Video

MIT SHAPESHIFTING

http://vimeo.com/79179138

Example• A fitness center offers an exercise program for anyone who

want to participate. The gym does a fitness test (using a treadmill) and gives out a personality questionnaire. They find there to be a moderately strong, positive correlation between fitness score and score of self confidence.

• What does the last sentence mean?

• Do you think the result is caused by causation, confounding, or common response?

HW • Complete the quiz. • Read 4.3