Zero mean of the error term conditional on the independent variable: Clearly state whether there is the potential for an omitted variable to impact the estimated slope coefficients in your regression analysis. If there is the potential for an omitted variable to the impact the results, give an example of the omitted variable and state whether it may bias the estimated slope coefficients in a positive or negative direction (see Table 2 on page 9 of the "Class Notes - Simple Linear Regression" document for an explanation of how to identify the direction of a potential bias from an omitted variable)