For the OLS Estimator = ( X)-1

question 15

Essay

For the OLS estimator = ( X)-1 Y to exist,X'X must be invertible.This is the case when X has full rank.What is the rank of a matrix? What is the rank of the product of two matrices? Is it possible that X could have rank n? What would be the rank of X'X in the case n<(k+1)? Explain intuitively why the OLS estimator does not exist in that situation.

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Definitions:

Rehearsal

A strategy for remembering that usually involves continuing to actively process to-be-remembered material, like repeating it to oneself.

Working Memory

The part of the cognitive machinery that holds information one is actively thinking about at the moment; also referred to as short-term memory.

Retrieval

What we usually mean by remembering, that is, getting information out of mental storage so we can use it.

Script

A schematic representation of the typical features of an event and the order in which they happen.