That would be gross to figure out, but I think - in a game - you can count on any scry effect you have as an additional card for probability purposes.How would scry affect HGD. Looking in regards to making land drops.
So if you have a 20 land deck and your opening hand is 2 Scry lands and you want to know what the chances are that you'll hit a 3rd land by turn 3, you'd plug these numbers into the Hypergeometric Calculator:
Pop: 60
# of Successes in Pop: 20
Sample Size: 11 - number of cards in opening hand (7) + number of cards you'll draw by turn 3 (2) + number of additional cards you'll see from Scry (2)
# of Successes in Sample: 3
For a 79% probability of having a 3rd turn land drop - up from 64% without the two Scry lands.
As for how
you'd factor in the chance that you'll get a Scry land and it'll then help you get your land drops...
Maybe find the probability of drawing each Scry land and add that to the card's "weight"? Like if you had a 16% chance of drawing a Scry land by turn 2 then each Scry land in the deck would count as 1.16 lands when figuring if you can hit your 3rd land drop?
That's a bit advanced for me, though. I think I'd rather just play a stable mana base without taking Scry into account and just count any instance of it as a bonus.