Fri Nov 4, 2016

Recall

  • Say its the early 1900's, and you are a statistician and you meet someone who claims to be able to tell by tasting whether the tea or the milk was added first to a cup.
  • You call BS and think they are just guessing.
  • Say you have 8 cups, tea, and milk handy. How would you design an experiment to test whether a) they can really tell which came first or b) they are just guessing?
  • Brainstorm all the components of this experiment with your seatmates. To revisit later: Then think about how you can implement this with resampl()ing.

Let's pick some pods at random…

Randomness

We'll view randomness in this course largely through two lenses:

See blackboard notes.

Explanatory and Response Variables

A medical doctor pours over some his patients' medical records and observes:

People who do this: Wake up with this:
Drawing Drawing

Explanatory and Response Variables

He then asserts the following causal relationship:

  • Explanatory AKA treatment variable: sleeping with shoes on
  • Response variable: causes one to wake up with a headache

What's wrong?

Diagram:

See blackboard notes.

Mantra of Statistics

Two Types of Studies

See blackboard notes.

Asserting Causality

  • Making causal statements with observational studies is harder because you need to control for (account for) all possible confounding variables; in this case alcohol.
  • But you may not have access to all confounding variables.
  • Prof. Caitlin Myers' "ECON 212 Empirical Economic Research" this Spring will study methods that attempt to make causal statements despite only having observational data.

Back to Example

  • The treatment, sleeping with shoes on, was NOT assigned at random; we have an observational study.
  • We can't assert causation, but only association/correlation
  • Instead
  • Say for each patient you have two variables: 1) whether they slept with shoes on and 2) whether they woke up with a headache
  • To assert causality, we would need a randomized experiment!

Principles of Designing Experiements

See blackboard notes.

Today's Learning Checks

I went to grad school in Seattle, where Garfield High School is located. Famous alums include:

  • Quincy Jones: Producer and composer
  • Jimi Hendrix: Guitarist
  • Brandon Roy: Former NBA Rookie of the Year
  • Macklemore: Rapper
  • Minoru Yamasaki: World Trade Center architect

Today's Learning Checks

Next door is Ezell's Fried Chicken. Oprah Winfrey apparently has it flown into to Chicago.

Drawing

Today's Learning Checks

One day I was raving about Ezell's Chicken. My friend Nick accused me "buying into the hype".

So what did we do?

Today's Learning Checks

Fried Chicken Face Off:

Do people prefer this? Or this?
Drawing Drawing

Today's Learning Checks

Say you have 12 grad students eager to procrastinate, how would you design a taste test to ascertain, independent of hype, which fried chicken tastes better?

Use the relevant principles of designing experiements from above.