In this lesson, you will learn how probability can be used to make decisions or predictions. We often use probability to make predictions in everyday life. If a weather forecaster predicts a high chance of rain, we make a decision to carry an umbrella or wear a raincoat. Those diagnosed with a high probability of heart disease make decisions to alter their life habits. Coaches use experimental probabilities to make decisions about their athletes. You simply use the probability of an event occurring to set up a proportion for many predictions. Using probability to make educated predictions is more accurate then random guessing.
Example
Angela owns a store that sells socks and other clothing. She needs to restock her socks and wanted to know the color preferences of her customers. Angela recorded the colors of the last 100 pairs of socks sold. She can use this information to make a prediction about how many socks of each color to order. Angela needs to order 1000 pairs of socks. How many of each color should she order?
| PAIRS OF SOCKS SOLD | |
|---|---|
| COLOR | NUMBER |
| Black | 9 |
| Blue | 20 |
| Yellow | 6 |
| Purple | 22 |
| Green | 25 |
| Red | 18 |
Set up a proportion: 
She should order 90 pair of black socks.
Set up a proportion:
She should order 200 pair of blue socks.
Set up a proportion: 
She should order 220 pair of blue socks.
Get the picture? Why don’t you finish finding the order amounts for the yellow, green and red socks? (Answers: 250 green pairs, 180 red pairs, 60 yellow pairs)
Making Predictions Practice
1. The experimental probability of Maura shooting a goal in field hockey is 12%. Out of 300 shots, about how many could she predict she would make?
2. If Scott flips two quarters 25 times, about how many times can he expect to flip two heads?
3. The Thorntons are planning a 12-day skiing trip during their winter vacation in December. The area they have selected gets the perfect conditions for skiing 23 days during the 31-day period. The Thorntons would like to spend at least 8 days skiing. Will their destination be a good choice?
4. The experimental probability that Ishika can throw a football through a hoop is 60%. How many throws out of 20 can Ishika predict she will make?
5. Lynn rolls a game cube 24 times. How many times can she expect to roll 1?
6. The theoretical probability of rolling a 1 or 2 is 1/ 3. How many rolls in 15 can you expect to be a 1 or 2?
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