To illustrate the concept of probability to your third-grade class, you will need to provide a few basic materials. Spinners can be found in some board games and they make a good start for teaching probability. However, you also will need to locate spinners that have an unfair balance. Choose several spinners that contain the same number of each type of section, such as a color or number. Try to locate some wipe-board spinners to create unfair spinners by making some sections larger or using the same color more than once. If you can't find wipe-board spinners, make your own from cardboard and construction paper or cover game spinners with construction paper to create an unfair advantage for certain colors or numbers. You may also want to provide your students with a chart.
Before you begin a lesson on probability, talk to your class about how probability works and how students can predict probability. Ask your students questions to determine how well they understand the concept before you begin. For instance, show them a spinner that contains four equal sections in different colors. Ask them what the probability is of spinning each particular color. If the class does not seem to understand the concept, spend time making sure each student understands before moving on.
Once the class has a grasp on the concept of probability, place the students into several groups, giving each group one fair spinner, one unfair spinner and a chart. Ask each group to predict the probability for each spinner. Then instruct them to spin each spinner 20 times and record the results on their charts. Once all of the groups are done, you can either compare the charts for each group or combine the results for more accurate results.
After all of the groups have completed the experiment portion of the lesson, it is time to help the class develop conclusions based on the information they collected. Talk about the accuracy of each group's predictions versus the actual outcome. Determine how close the predictions actually were. You may also want to ask each group to explain how they reached their predictions. Illustrate the group results on the board at the front of the room so the students can clearly see the outcome for each group and how they relate to each other. Compare the results on the fair and unfair spinners to show how unfair spinners still provide consistent results, though the results are often skewed toward the larger or more numerous sections.