MDF and Alpha

Overview

Now that we have a foundational understanding of betting and range composition, it is time to explore MDF and Alpha: the thresholds for calling and bluffing.

What is MDF

Minimum Defence Frequency (MDF) is the minimum frequency at which you must defend (call or raise) against a given bet size to remain unexploitable. If you fold too much in any given spot, your opponent can profitably bluff any two cards. To avoid being run over by bluffs, you must call at least as much as the MDF frequency.

What is Alpha

Alpha is the minimum frequency that your opponent must fold against a given bet size for your bluff to break even. If your opponent calls too much in a given spot, you should not bluff. If they fold too much, you should bluff. To decide whether it is profitable to bluff in a given spot, just ask yourself if your opponent is folding more or less than alpha.

Calculating MDF and Alpha

Alpha is computed as risk / (risk + reward)

If you bluff with a bet of 50 chips into a pot of 100 chips, your bluff only needs to work 33.3% of the time to break even.

MDF is computed as reward / (risk + reward) or simply 1 - Alpha

If your opponent bluffs with a bet of 50 chips into a pot of 100 chips, you must defend at least 66.6% of the time. Otherwise, your opponent can take advantage of the fact you are folding more than alpha and have a profitable bluff with any two cards.

Takeaways

MDF is important for understanding the underlying concepts: fail to defend enough and you can be exploited with bluffs. However, if your opponent is not going to exploit you by bluffing any two cards, then you do not necessarily have to defend at the MDF frequency. If they are underbluffing, you should be overfolding.

Alpha is a useful tool regardless of the opponent. It simply computes the frequency at which your opponent needs to fold to make your bluff profitable. It is your job to decide whether they are folding enough to make your bluff profitable.