ASSIGNMENT 1 2025
UNIQUE NO.
DUE DATE: 16 MAY 2025
, ECS4863
Assignment 1 2025
Unique Number:
Due Date: 16 May 2025
Advanced Econometrics
Question 1
1.1 Explain the concept of omitted variable bias and distinguish between positive
and negative bias. (4 Marks)
Omitted Variable Bias (OVB) occurs in regression analysis when a relevant variable
that influences both the dependent variable and one or more independent variables is
left out of the model. This omission violates the assumption that the error term is
uncorrelated with the regressors, leading to biased and inconsistent estimates of the
coefficients.
For OVB to occur:
1. The omitted variable must be a determinant of the dependent variable.
2. The omitted variable must be correlated with one or more included independent
variables.
Positive Bias arises when the omitted variable is positively correlated with both the
dependent variable and the included independent variable. This leads to an
overestimation of the effect of the included variable.