In response to the recent post about the comparative success of short and deep passes a few readers asked for a break out of the results by down. Some suggested the advantage of deep passes might only due to unsuccessful check downs on 3rd down, which is certainly plausible. The numbers are going to be slightly different here because I neglected to exclude red zone attempts in the original post. (Please read the original post for definitions and caveats.)
Here is the break out by down. It appears that the advantage exists on all downs, and the advantage is not significantly greater for 3rd downs than for 1st or 2nd downs. But that doesn't necessarily rule out the check-down effect, as they are a common tactic on all downs.
But not all 3rd downs are the same. Here is the same break out of EPA by down, but limited only to 10 yards to go. This isolates the 3rd and long situation from other 3rd down attempts, but just because the to-go distance is the same doesn't mean the situations are the same. The difference between deep and short attempts is larger on 3rd and 10, but it's nearly as large on 2nd and 10.
And again for only 5 yards to go. Keep in mind 1st and 5 situations are relatively scarce. For that matter, fourth down attempts for all to go distances are relatively scarce too, as the data are restricted to 'normal' situations--1st and 3rd periods with the score within 10 points.