# An Introduction to Probability

## Introduction to Probability

Hi everyone, thanks for watching this video tutorial on probability problems.

Now, even the simplest of probability problems can quite frequently make us feel a little uncomfortable and intimidate us, but there’s no reason that they should do that.

They’re pretty simple once you break them down, so let’s go over the rules together and then we can try a practice problem.

The most basic way to explain probability is using division, where the number of desirable outcomes is divided by the number of all possible outcomes—number of desirable outcomes over the number of all possible outcomes.

For example: I have a little paper cup here and it has different colored houses—blue ones, red ones. I like the blue ones better, but there are only 3 of those. There are 5 red ones.

Now, if I wanted to draw 1 randomly out of this little cup, what are my odds of getting a blue one? Which is what I want.

Well, remember in a probability problem we use division, and if I want 1 of the blue ones, there are only 3 of those—that’s the number of desirable outcomes, over the total number of outcomes—which is 8, because there are 8 little houses in this little cup.

Let’s try to draw 1 randomly and see what happens. What do you know, a red one! That’s not what I wanted, but if I take it out and I leave it out, and then I draw again, my probability will have changed because there’s no longer 8 little houses in this cup, there are only 7, and there are 3 blue little houses that I want.

Let me draw 1 more time and see what happens. Here we go, blue. What changed? Well, nothing with regards to our blue house number, remember it’s still 3, but now it’s over 7 because that’s the total number of houses after I drew out that 1 red one, so my odds got better as I started drawing out alternative choices from the little cup.

Make sense? I hope that helps. Thanks for watching this video tutorial, and until next time, happy studying.

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by Mometrix Test Preparation | Last Updated: September 17, 2019