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# lec2

last edited by 12 years, 6 months ago

survey questions from lecture 2

 Q: I am not familiar with the {} notation - could provide a brief explanation? Thanks! A:(Ted) { } could mean different things.  Here I am using it to denote the variance function.  I.e., var{x}=sum of (x-mean x) quantity squared.  (ask me in class if this isn't clear) Q: I am unsure how to approach the proofs. Should I feel comforted by their existence, as I now know for sure that what we are working on has a basis in logic, or should I try to learn/do them?   A(Ted): I would say yes...see if you can follow the steps of the proofs.  Some are more important than others.  For example, if you understand the proof for the variance of b1, then you are likely to retain the concept of where the standard error of regression coefficients comes from. Q: using this command in stata (from lab assignment 1 sheet) -collapse (mean) occ_fem=sex occ_ave=wage (count) occ_n=sex, by (occ)- occ_fem is supposed to be the proportion of women in the occupation, right? If so, how does STATA know only to pull the female values from the sex var?   A(Ted): it is just calculating the mean of sex by occ.  I.e., just as someone might calculate the percent hispanic by state etc.  So it is just taking averages. Q: What is the NWK book that the slides often refer to? Is this something we need to read in addition to the online text? A:(Ted) Netter, Wasserman , and Kutner, Applied Regression Analysis.  A standard book  for a course like this.  You do not need to read it, but I have referenced it when I have used it to write the lectures.