a. b. C. d. e. f. Explain what are unobserved heterogeneity in panel data analysis? Provide a real example of unobserved heterogeneity? Define the two basic approaches to modelling the unobserved effects in traditional panel data analysis. How to determine whether the fixed effect model or random effect model is more appropriate? Explain how to conduct the above test (in d.) and state the null and alternative hypothesis of the above testing? What are the main reasons to use the generalized methods of the moment (GMM), estimator?