Do 400 of 1000 sales signal a favourite plan

A streaming service sells three subscription plans $A$, $B$ and $C$. Among its first $1000$ sales, $400$ were plan $A$. Does this show customers prefer plan $A$ (i.e. its share exceeds one third)? Reply $1$ for yes, $0$ for no.

$1$ (yes). Under equal preference $p=\tfrac13$, the standard error of $\hat p$ is $\sqrt{\tfrac{2/9}{1000}}\approx0.0149$, so $z=\tfrac{0.4-1/3}{0.0149}\approx4.47$. The one-sided p-value is a few in a million, so equal preference is rejected.