Let $(\mathcal A,\varphi)$ be a noncommutative probability space, where $\mathcal A$ is a unital associative algebra and $\varphi:\mathcal A\to\mathbb C$ is a tracial state, meaning that $\varphi(xy)=\varphi(yx)$ for all $x,y\in\mathcal A$. Then for every $k\in\mathbb N$ and every $a_1,\dots,a_k\in\mathcal A$,