Friday, February 27, 2009

Possibilities vs. Probabilities

Citizens of the Junior High: The PSSAs are coming soon. That can only mean one thing:

Free breakfast.

You've probably heard the saying, "There's no such thing as a free lunch." Well, that's because there are way too many possibilities for breakfast.

Lets's consider the options you had for choosing your breakfast: Orange or apple juice (much to the dismay of Mathman, espresso isn't one of the options here) and a breakfast item of a Cocoa Puffs cereal bar, Trix cereal bar, cinnamon sugar donut, apple, banana, or the ubiquitous "Honey Bun".

If we were to quickly calculate the possibilities for the number of breakfasts we'd have:

Orange juice and Cocoa Puffs cereal bar
or Trix cereal bar
or cinnamon sugar donut
or apple
or banana
or "Honey Bun"

Apple juice and Cocoa Puffs cereal bar
or Trix cereal bar
or cinnamon sugar donut
or apple
or banana
or "Honey Bun"

So there are 12 possibilities for breakfast.

There's a simpler way of finding out how many ways to choose breakfast. Think about it 2 ways for juice, 6 breakfast items = 12 possibilities.

2 and 6 to get 12. Multiplication must be the secret operation.

Now, we can also consider that picking a juice doesn't effect the choice of a menu item. So choosing a juice and a breakfast item are independent events.

Now that we have considered the possibilities, let's consider the probability of choosing a particular breakfast. Let's look for P(apple juice, Trix cereal bar). The P() stands for probability of what's in the (). The P(apple juice, Trix cereal bar) is 1 result of 12 possibilities or a 1/12 chance. We could also get here by taking the P(apple juice)= 1/2 and P(Trix cereal bar) = 1/6. Once again, use the secret operation of multiply to get 1/12.

So the odds of getting Mathman's favorite breakfast of espresso and chocolate chip and banana pancakes is P(espresso, banana pancakes) = 0*0 = 0 since the P(espresso)=0 and the P(banana pancakes)=0.

Let's end on a positive note: the P(staying radical)= 1 or 100%. That's the only way to be.