2-ofs

Three weeks ago we discussed Hypergeometric Distrubtion and introduced this series. We also discovered that if you run four copies of a card in a 60-card deck you have a 40% chance of having at least one copy in your opening hand.

Here is the introduction: http://mtgolibrary.blogspot.se/2015/12/1-ofs-2-ofs-3-ofs-and-4-ofs-and.html

This week we are talking about 2-ofs. As an example we will be using Rolling Thunder in Pauper RUG Tron.

The Hypergeometric Distrubtion calculator from part 1 shows us that the probability of having at least one Rolling Thunder in your opening hand (if you run two Thunders) of 7 cards is 22%.

Here we have to consider another factor. By turn 6 you have a 5% chance of drawing multiple copies of your 32of card. This is significantly less than a 3-of card (12%) which is an important factor for cutting down to two copies of a card like Rolling Thunder.

So when do you run 2 copies of a card in your deck?

You want to be sure that you can draw one copy of the card in the midgame or the lategame
This card is good and you want to see a copy of if the game goes long.

You do want one (and often exactly one) Rolling Thunder to stabilize the game or finish the opponent.

This is the major case for running a 2-of. Grim Harvest in UB Trinket Control.

Be aware that if you go down to one copy there will be many games where you never see the card at all, making it quite random. We will talk more about that next week.

Getting the second copy of your card in hand suffers from diminishing returns
As stated above the chance of drawing a second copy of your card increases by 150% if you run three copies of your card. If there is any sort of diminishing returns from your card (as with our Grim Harvest and Rolling Thunder examples above) it is a significant mistake to run three copies of the card. Run two copies.

You really want to run 6 copies of a card
If you have a card that is a 4-of and you then want two additional copies that means that the second card has to be a 2-of.

You need to run 2 copies for mana curve considerations
If your mana curve needs exactly two cards of this cost you have a good case for a 2-of.

Getting the second copy of your card in hand is not a total disaster
If you draw your second Rolling Thunder after you have saved yourself in the midgame you can use that one as a finisher or you can hit the opponent twice. If the second copy of the card is totally meaningless even in the lategame you should consider cutting the second copy.

I have a hard time thinking of an example of this. Generally, 1-ofs that are not searchable are mistakes and should be 2-ofs.