Upgrade to remove ads
Week 6 - Polynomial regression models, Multicollinearity, Variable Transformation
Terms in this set (23)
A regression model for non-linear relationships; a curvilinear correlation coefficient is computed
The bigger the difference in ____ the better the model's fit over the previous one.
B0 in polynomial
B2 in polynomials
The parabola'' concavity. If B2 > 0, the curve opens upwards. Whereas the parabola is convave B2 < 0
Interaction in polynomials
Second Order Polynomial
Also called cuadratic
A situation in which several independent variables are highly correlated with each other. This characteristic can result in difficulty in estimating separate or independent regression coefficients for the correlated variables.
Problems with multicollinearity
Coeffficients cannot be interprated due to unreliable estimates, mainly because of their standard errors.
Signs of the coefficients are not reliable. Usually, are the opposite of that one could expect theorethically.
Statistical tests are biased. t tests and global tests are contradictory.
Variance Inflation Factor (VIF)
a method of detecting the severity of multicollinearity by looking at the extent to which a given explanatory variable can be explained by all the other explanatory variables in the equation
- Symetrize distributions
- Stabalize spread
- Linearize relationships between variables
- Normalize distribution
Types of transfromations
Best tool for verifying departures from normality
Negative skewness (QQ)
Powers (and roots) lower than 1
Positive skewness (QQ)
Powers (and roots) logreaterwer than 1
Low Level of Multicollinearity
1 < VIF < 5
Medium level of multicollinearity
5 < VIF > 10
High level of multicollinearity.
10 < VIF
Alternative to VIF
Center and Standarize
What to do when multicollinearity its found.
y increases n for every 1 unit increase of x
y ~ income or poly(x,2)1
What would be the prediction based on this formula's output?
y increases n for every 1 unit squared increase of x
y ~ poly(x,2)2
The shift of the parabola. It shifts towards the right when theBcoefficient's value is greater.
Sets with similar terms
Business Stats final
Econometrics Exam 2
eco stat ch 17
Other sets by this creator
Week 11 - Logistic Regression
Week 8 - Linear Model Validation
Week 5: Attention
Other Quizlet sets
Criminal Justice Exam 2
Neuroscience Chapter 5
PSYCH 3400 CH 1
Chapter 12: Be able To