Knight promotion is the second most common promotion. Most of the time it is to give an otherwise undeliverable check. But it doesn’t always come with check. Statistically speaking, what percentage of knight promotions come with check and percentage doesn’t come with check?
ChessBase allows you to search for positions with promotions to each piece, with or without check. In the Mega 2019 database, there are 8,266,473 games.
In those games, there are 486,622 promotions to queen; 7,223 promotions to knight; 1,486 promotions to bishop; and 9,606 promotions to rook. Of the 7,223 promotions to knight, 5,733 came with check, or 79.3%. Bonus: Of the 5,733 knight promotions with check, 106 were mate on the move.
Of course, Mega does not have every game, but this can give you a pretty close idea.