Marginal probabilities refer to what?

Marginal probabilities are the probabilities of each individual event occurring in isolation, without consideration of any other events. This means that if you are looking at a probability distribution, the marginal probability gives you the likelihood of an event happening when you sum or integrate over the probabilities of all other related variables or events.

In contrast, the total probabilities of two combined events pertain to joint probabilities, which are calculated considering the occurrence of both events. Joint events involve more than one random variable simultaneously, whereas marginal probabilities focus solely on individual events.

As for the probabilities considered within the sample space, this refers to the total probability distribution for all possible outcomes, which encompasses both marginal and joint probabilities. However, marginal probabilities specifically highlight the likelihood of each separate event occurring on its own, making the definition of marginal probabilities distinct and clear.