A bet does not start from "I like it". It starts from a number. The process has four steps and each one can say "no".
The four steps
- Get the fair market probability by removing the margin.
- Estimate your own probability from data (form, absences, a model).
- Play only if the price beats the fair one by a threshold you set in advance.
- Set the stake in units, with a fraction of Kellyi or a flat percentage.
The gap from 50.7% to 54% is your edge. If your estimate were 51%, the edge would be only 0.3 points and inside the model's error. The right call there is not to play.
The threshold and the stake
You set the threshold before you see the match, e.g. "I only play if my estimate beats the fair probability by 3 points". If you change it every time, you do not have a process, you have a mood.
With an edge of 3.3 points at 1.90, the Kelly formula gives f = (b·p − q) / b, where b = 0.90, p = 0.54 and q = 0.46. That is (0.486 − 0.46) / 0.90 = 2.9% of the bankrolli. We play a fraction, say a quarter, which is about 0.7u. The fraction protects you from an error in the estimate.
Why we skip most matches
The market is a tough opponent. In many matches there is no gap worth taking. Not playing is part of the strategy, not a failure of it.