What is experimental probability?

Experimental probability is the probability of an event happening when you actually conduct an experiment.

Your results may not always be what you expect and they may be different every time, but overall you should see that the results tend to be close to what you would expect.

Example 1:

What is the experimental probability of getting heads when flipping a fair coin 10 times?

 In order to answer this question, you would have to take a coin, actually flip it 10 times and see what you get.  Here are sample results, use them to answer the question.

H H T H T T H H H T

There are 6 heads and 4 tails.

So, the probability of getting heads is 6/10. 6 is the number of heads, over 10, the total number of trials.

Always reduce fractions to lowest terms, so 6/10 would be 3/5.

The experimental probability of getting heads is 3/5 or 0.6 or 60%

Try this again with your own coin.  Did you get the same answer?

Example 2:

What is the experimental probability of rolling a 4 with one 6-sided die 10 times?

In order to answer this question, you would have to take a die and roll it 10 times to find your result.  Here are sample results, use them to answer the question.

2 5 3 4 6 2 1 4 2 2

There are 2 fours.

So, the probability of rolling a four is 2/10, or 1/5 when reduced.

The experimental probability of rolling a four is 1/5 or 0.2 or 20%.

Try this again with your own die.  Did you get the same answer?

If you did not get the same answer when you tried either of the experiments that is ok, actually that is expected when you do an experiment like this.  That is why we call it Experimental Probability.

All probabilities are written as fractions with the number of positive outcomes on top and the total number of trials on the bottom.

Probability of event = (# of positive outcomes)/(# of trials)

You can always take your fraction and rewrite it as a decimal or percent.

If you are ready to test your knowledge of experimental probability,