Study Guide

Predicting vs. Observing Probability

Predicting vs. Observing Probability

There are two ways to calculate probability: 

  • using math to predict
  • by actually observing the event and keeping score.

Theoretical probability uses math to predict the outcomes. Just divide the favorable outcomes by the possible outcomes.

Experimental probability is based on observing a trial or experiment, counting the favorable outcomes, and dividing it by the total number of times the trial was performed.

Let's look at this example: we tossed a coin 36 times and recorded the outcomes:

H, T, H, H, T, T, H, T, T, T, T, T,
T, T, T, H, H, T, H, H, T, H, H, H,
H, T, H, H, T, H, H, T, H, H, T, H

Based on this experiment:

  • Experimental probability of flipping Heads is  or about and Tails is  or about 
  • Theoretical probability of flipping Heads is and Tails is