Introduction to Conditional Probability

In this lecture we present the basic definition of conditional probability, and examine a few problems that illustrate how conditional probabilities can be computed and manipulated for making decisions and inferences in uncertain environments.

[shantnukakkar]

Example 3 doesnt make sense intuitively. If we know that outcome is head then we can have either coin 1 or 3. That means there is a 50% chance that the other side is head (if its coin 1) and 50% chance that other side is tail (if its coin 3). So, shouldn't the answer be 1/2?