1 / 12

2004 QE1 Statistics Review

2004 QE1 Statistics Review. Adam Shrager ashrager@yahoo.com ashrager@princeton.edu April 4, 2004. First, the disclaimer…. I have not seen this year’s exam Everything is subject to change Consider the following direction in the realm of highly probabilistic based on prior (recent) exams.

dale
Download Presentation

2004 QE1 Statistics Review

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. 2004QE1 Statistics Review Adam Shrager ashrager@yahoo.com ashrager@princeton.edu April 4, 2004

  2. First, the disclaimer… • I have not seen this year’s exam • Everything is subject to change • Consider the following direction in the realm of highly probabilistic based on prior (recent) exams. • In terms of focusing your studying efforts…there are some pretty clear guidelines….

  3. The three types of Statistics Questions on the QE1 • The Regression Question • Explain the model • Calculate something • Analyze or criticize the model • The Hypothesis Testing Question • Often difference of means or proportions • Your choice: Confidence interval or t-test • The Probability Question • On May ’03 exam. • Bayes Rule (Conditional Probability)

  4. The Regression Question • Explain the Regression Equation What are we modeling? Restate dependent and independent variables. What does one additional unit of X do to Y? Get specific. May ’02: “ A one mpg increase in avg. fuel efficiency will lower the per capita oil consumption by 0.38 barrels per person per year.”

  5. The Regression Question • Plug numbers into the model to solve for something. May ’02: 3 mpg increase lowers oil consumption by 1.14 barrels per person per year (0.38 x 3). With 260 million people, change in national oil consumption would be 296 million barrels per year (260,000,000 x 1.14). Question asked for you to explain the 296 million barrel claim.

  6. The Regression Question • Criticize/Analyze/Discuss the model • CORRELATION!!!!!!! • External validity • What else impacts Y? • Use “external” knowledge (or knowledge gleaned from background reading) here.

  7. Hypothesis Testing • Be prepared for: • Difference of Means • Difference of Proportions Have these formulas handy!!!!! Consider: “Do I like confidence intervals or do I like t-tests?”

  8. Hypothesis TestingTIPS FOR SUCCESS • Make and explicitly state your assumptions. Even if wrong, then your answers will logically flow. • Assumptions: • State Null (H0) and Alternative (Ha) hypothesis • Two-sided/one sided test • Level of confidence (often .05) • What test are you using and why?

  9. Hypothesis TestingTIPS FOR SUCCESS • Be sure to explicitly test for (and state that you are testing for) the following: • If confidence interval, is zero in the interval? Why does this matter? (also common: if asking about “majority,” is .50 in the interval?) • If t-test, explicitly state critical value (often 1.96 or 1.68, could be something else). Does your test statistic exceed this value? What does that mean? Even if you screw up the math – by explicitly stating what you’re doing, the grader can follow your logic and may only deduct nominal points. • If you use both tests – do your answers correspond? THEY SHOULD!!!!!!!!!

  10. Probability • What could they ask you? • Conditional Probability • Bayes Rule. • It’s your choice…..

  11. Bayes Rule • The algebraic formulation for Bayes’ Rule • P (A│B) = P (B│A) P (A) / P (B) (plug in the numbers presented to you as appropriate, and solve)

  12. Bayes Rule • Much easier to solve with a tree.

More Related