How to Calculate Probability With One Sample

A simple example makes probability easier to understand.

The science of probability deals with calculating how likely certain events are to occur. Probability calculations can get complicated, and are sometimes completely unintuitive. But the basic calculations are not difficult to understand, especially if you work with a simple example.

Instructions

1. Count the total number of possible outcomes. For example, suppose you want to figure out the probability of getting a 10 or higher when you roll two dice. There are six possible sides the first die can land on, and for each of these possibilities there are six sides the second die can land on. This makes a total of 36 possible results.

2. Count the number of outcomes in which the event takes place. For example, there are six possible combinations of two dice that add up to 10 or more: 4-6, 5-5, 5-6, 6-4, 6-5, and 6-6.

3. Divide the number of matching outcomes with the total number of outcomes. This is the probability the event will take place. For the example above, you would divide six (the number of rolls that are at least 10) by 36 (the total number of possible rolls). The result is 1/6, or 16.66 percent.

References

• "Everyday Mathematics: Student Reference Book;" 2002