The OLS Slope Estimator Is Not Defined If There Is

question 52

Essay

The OLS slope estimator is not defined if there is no variation in the data for the explanatory variable. You are interested in estimating a regression relating earnings to years of schooling. Imagine that you had collected data on earnings for different individuals, but that all these individuals had completed a college education (16 years of education). Sketch what the data would look like and explain intuitively why the OLS coefficient does not exist in this situation.

---

Definitions:

Primary Bronchi

The major air passages that branch off directly from the trachea into each lung.

Larynx

A complex structure in the neck involved in breathing, producing sound, and protecting the trachea against food aspiration.

Esophagus

The muscular tube that connects the throat (pharynx) with the stomach, allowing for the passage of food.

Trachea

The windpipe, a tube that connects the larynx to the bronchi of the lungs, providing a path for air to enter and exit the lungs.