# Differences in coefficients

Suppose I want to see whether $z$ is a confounder for a model with $y$ the outcome variable and $x$ the predictor. If I adjust for $z$, and the adjusted coefficient of $x$ changes versus the unadjusted coefficient of $x$, does it matter by how much it changes? If the difference between the unadjusted and adjusted coefficients for $x$ is very small, should I still take this into account?

-