Math Math Math!
Simple, straightforward math help!
We can use probability trees to help understand probabilities even more.
Let's try an example ...
Imagine a town where 60% of the cat population are short haired cats and 40% are long haired cats.
Long haired cats have fleas with a probability of 35%, whereas short haired cats have of probability of 20% of having fleas.
Calculate the probability that a cat, picked at random has fleas.
So, there will be short haired cats & long haired cats with fleas.
The probability that a cat picked at random is short haired and has fleas is ...
Probability = 60% x 20%
The probability that a cat picked at random is long haired and has fleas is ...
Probability = 40% x 35%
To find the probability that a cat picked at random will have fleas we just add together these two values ...
In fact to calculate the probability that either event A will happen OR event B will happen we add the probability of each event together, so ...
Probability of event A OR event B happening = Probability of event A + Probability of event B
So, probability that a cat picked at random will have fleas = 12% + 14%