Unit 1 Reading o Directions: There are 3 passages in this unit. Each passage is followed by some questions or unfinished statements For each of them there are four choices marked A), B), C)and
Choosing a Topic Start with a general area or set of questions Make sure you are interested in the topic Use on-line services such as EconLit to investigate past work on this topic Narrow down your topic to a specific question or issue to be investigated Work through the theoretical issue Economics 20-Prof. Anderson
Why Use Instrumental Variables? e Instrumental Variables(IV)estimation is used when your model has endogenous xs That is, whenever Cov(x,l)≠0 Thus. i can be used to address the problem of omitted variable bias 2 Additionally iv can be used to solve the classic errors-in-variables problem Economics 20- Prof anderson
Dummy variables a dummy variable is a variable that takes on the value l or o Examples: male(= 1 if are male, O otherwise), south(=l if in the south, 0 otherwise), etc dummy variables are also called binar variables. for obvious reasons Economics 20- Prof anderson
Assumptions of the classical Linear Model (Clm) e So far, we know that given the Gauss Markov assumptions, OLS IS BLUE e In order to do classical hypothesis testing we need to add another assumption(beyond the Gauss-Markov assumptions) Assume that u is independent of x,x2…,xk and u is normally distributed with zero mean and variance 0: u- Normal(0, 02) Economics 20- Prof anderson
Some Terminology o In the simple linear regression model where y=Bo+ Bx+ u, we typically refer to y as the a Dependent variable, or a Left-Hand Side Variable. or Explained variable, or Regressand
Microbial growth Conditions 1. Macronutrients 2. Micronutrients 3. Growth factors 4. Environmental factors: temperature; pH; Oxygen et al Nutrient requirements Microorganisms require a bout ten elements in large quantities, bec
