HOH question (help plz)

Just been reading through vol I again and came across something i didnt quite understand (must have overlooked it before), its about calculating expected value more precisely (last page on pot odds in part four) quote:

"To be more precise in your calculation multiply the size of your intended bet by the probability he will call it"

OK first part of formula is easy to obtain, but i am having problems figuring out how to get a figure for probability he will call, ingame i can calculate a rough edge on whether or not someone will call what bet i make (using reads etc) but for the life of me i cannot understand how to turn this into a figure exact enough for the formula, i certainly must be missing something here can someone plz explain this? Thanks in advance and sorry to bother you people with this basic stuff

The precise way would be to put villain on a range of hands, then split that range into a 'folding range' and a 'calling range' and use the appropriate figure (ie. if his calling range constitutes 40% of his total range then the probability of him calling is 0.4).

In practice, given that you have like 30 seconds to make a decision online it's not going to be possible to do this precisely, so you have to go with a best estimate.

Let's say we're looking at a Qd9d3h6c board and villain has called our preflop raise and flop lead (our cards don't matter for the sake of this). We can probably put an average small-stakes villain on something like QT+/JT/99/33/JJ-TT/mid-high diamonds. Let's say we think if we make a 3/4 pot bet that villain will fold a bare flush draw, JJ-TT and JT and call with everything else. Off the absolute top of my head those hands probably constitute about 60% of his total range, hence the probability villain calls a turn lead is 0.4.

The above is really contrived, but hopefully you get the idea.

Thank you very much sir, i understand now

No problemo.

Card Player Magazine - Either He Was Winning, or I Was by Lee H. Jones

This article goes over what you were talking about.

I am also pretty sure Harrington goes over how to use ranges in a situation where he has AA and is trying to figure out whether to call his opponent (who has a set of 9's on the flop.)

might be a dumb question, but how would you figure out their range of hands? I know this would be easy online because you can take notes, but live how would you remember all of this information? Or is this probability based on what you think they might have?

There's no bona fide way of figuring a range out - there's always scope for error. You just have to operate with a best estimate from your knowledge of the player (notes obv help here). You can also narrow a person's range down throughout a hand. If a nit raises in early position you can assign a range of something like TT+/AK to them. Then if a flop comes K62r and we know (or suspect) that our nitty villain will only lead with top pair+, we can narrow his range to KK+/AK.

Another really basic and contrived example, but I hope it serves.

New title for you Dorkus.....Master Contriver!

As contrived as those were, they pretty much did the job.