Discrete Probability Distribution

An Example Discrete Distribution

We previously showed you a discrete probability distribution about flipping a fair coin three times. Let's look at this distribution again in more detail:

The chart shows the probability that none of the three flips was heads, one of the three flips was heads, two of the three flips were heads, or all three flips were heads. Notice the x-axis represents the number of times that heads showed up and the y-axis represents the probability of the result.

Discrete probability distributions can also be represented in tables:

Based on the above visualization, you can see a few interesting characteristics about discrete probability distributions:

• For all values on the x-axis, the y value is greater than or equal to 0.
• For each x, the probability p(x) is equal to the y value
• The sum of all y values is 1; there's a 100% chance that something will occur.

Here is what we mean by the sum of all y values is 1. When flipping a coin three times, there is a 100% chance that you will either get zero heads, 1 heads, 2 heads or 3 heads (ignoring the very very small chance that the coin lands on its side).

In the next part of the lesson, you will get practice working with a discrete probability distribution.