conditional probability

This term is used in the context of probability.

It’s associated with a dependent event, where the probability of a second event is affected by a first event.

For example, imagine that there are five apples in a bag – two red apples and three green apples. Every time an apple is taken from the bag, the probability of taking an apple of a specific colour changes, because the colour of the second apple depends on the colour of the first apple.

The probability of taking a red apple is \frac{2}{5}. After taking one apple, the probability changes.

Therefore, next time:

    • if a green apple was previously taken from the bag, then the probability of taking a red apple next time is \frac{2}{4}

    • if a red apple was previously taken from the bag, then the probability of taking a red apple next time is \frac{1}{4}.