what is the difference between P(AB) and P(A, B)?

CFA Level I
#1

from reading 8

what is the difference between joint probability P(AB) and joint probability function P(A, B)?

#2

They’re the same thing.

Different authors sometimes use different notation.

#3

they even listed these two as two glossary entries but.

Joint probability

The probability of the joint occurrence of stated events.

Joint probability function

A function giving the probability of joint occurrences of values of stated random variables. 

	<p>so they're exactly the same?</p>
</dd>
#4

Technically, the difference is that the joint probability function gives all of the probabilities for all possible values of the random variables (i.e., for all possible random events), while the joint probability is the value of the joint probability function for given (i.e., specific) values of the random variables.

It’s the same as the difference between the function:

f(x) = _x_²

and the specific value of the function when x = 2:

f(2) = 2² = 4.

For the purpose of the exam, there’s no reason to think of them as differing from each other: they’re the same thing.