# Math Help - Effect of singuar

1. ## Effect of singuar

Suppose I have:

$\theta=(X^\top X)^{-1}X^\top y$

What is the effect on the value $\theta$ if ( $X^\top X$) is almost singular?

2. Originally Posted by noob mathematician
Suppose I have:

$\theta=(X^\top X)^{-1}X^\top y$

What is the effect on the value $\theta$ if ( $X^\top X$) is almost singular?
What does "almost singular" mean? I assume that you mean $\det X^{T}X$ is small in modulus?

3. Yes that's what I mean. Does it make sense?