Previous midterms
Previous finals
Final exam review topics (from Winter 2023)
Chapter 6
- Why we need multiple “X” variables - OVB
- OVB: what it is, when it happens, and why
- house price/fireplace example
- How the formula for the $b$ are obtained
- Interpreting the $\beta$
Issues that arise in the multiple regression model:
- No perfect multicollinearity / DVT
- define it
- examples: different units/gender dummy/location dummy
- Imperfect multicollinearity - basic definition and consequences
- $R^2$ no longer works
- $\bar{R}^2$ used instead
Chapter 7
- Joint hypothesis test
- t-test can’t be used - explain why
- F-test
- Restricted/unrestricted models
- Why the F-test formula with $R^2_U$ and $R^2_R$ makes sense
- Identifying models under $H_0$ and $H_A$
- CIs don’t extend well for joint hypothesis tests (confidence sets)
- Overall F-test
- How/why to eliminate variables from a model (model selection/building)
- Presenting models in tables
Chapter 8
- Linear vs. non-linear effect
- Consequences of missing a non-linear effect
- Polynomial regressionn model
- Determine “r”
- Interpret the $b$ by predicting values ($\hat{y}$)
- Logs
- Can “linearize” exponential growth (GDP)
- Can “linearize” multiplicative models (Cobb-Douglas)
- approximate percentage changes
- 3 configurations: lin-log, log-lin, log-log
- Intepretations of the $\beta$ in these three configurations
Chapter 9
- Interaction terms
- $D \times X$ allows for different slopes/lines for different groups
- Test for differences between groups
- Dummy-dummy interactions
- different effect for different groups
- DiD
- minimum wage example
- fundamental problem of causal inference
- DiD estimator is the $b$ on the dummy-dummy interaction
- Picture
Chapter 10
- Hetroskedasticity vs. homoskedasticity
- What heterosked. and homosked. look like in a plot
- Implications of heteroskedasticity
- Fix for heterosked.
- Testing for het.
Chapter 11
- Missing variable problem
- Instrument, $z$, has two properties
- IV/2SLS - describe the two stages
- wage/education example
- demand example