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Econometrics I Summer 2011/2012 Course Guarantor : prof. Ing. Zlata Sojková, CSc ., Lecturer : Ing. Martina Hanová, PhD. Econometrics. Regression Specification Error Test Types of specification errors : • Omitted variables • Incorrect functional form
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Econometrics I Summer 2011/2012 Course Guarantor: prof. Ing. Zlata Sojková, CSc., Lecturer: Ing. Martina Hanová, PhD. Econometrics
RegressionSpecificationError Test Typesofspecificationerrors: • Omitted variables • Incorrect functional form • Correlation between X and e, Ramsey's RESET Test
Akaikeinformationcriterion Bayesian information criterion (BIC) or Schwarz criterion (also SBC, SBIC) Verification of the model specification
Heteroskedasticity occurs when the variance of the disturbance is not constant. • often encountered in cross section data • not affect the parameter estimates • bias the variance of the estimated parameters. • t-values for your estimated coefficients cannot be trusted. • Goldfeld–Quandt test • Breusch–Pagan test or LagrangeMultiplier • White test Heteroscedasticity
White test has become extremely widely used, the most powerful and most respected. Auxiliaryregression ei^2=b0 + b1*X1 + b2*X2 + b3*X1^2 + b4*X2^2 + b5*X1*X2 + ui White test
violationoftheordinaryleastsquaresassumptionthattheerrorterms are uncorrelated Durbin–Watson Breusch–Godfrey test or Lagrangemultiplier test Autocorrelation
occurs when two or more predictors in the model arecorrelated provide redundant information about the response Consequences: Increased standard error of estimates Often confusing and misleading results Multicollinearity
compute correlations between all pairs of predictors – correlationmatrix Farrar-Glauber Test calculation of the paired correlation coefficients Detecting multicollinearity