  We report quantitative measurements of the impact of alloy disorder on the
$\nu=5/2$ fractional quantum Hall state. Alloy disorder is controlled by the
aluminum content $x$ in the Al$_x$Ga$_{1-x}$As channel of a quantum well. We
find that the $\nu=5/2$ state is suppressed with alloy scattering. To our
surprise, in samples with alloy disorder the $\nu=5/2$ state appears at
significantly reduced mobilities when compared to samples in which alloy
disorder is not the dominant scattering mechanism. Our results highlight the
distinct roles of the different types of disorder present in these samples,
such as the short-range alloy and the long-range Coulomb disorder.
