Concept Byte: Probability Distributions

For Use With Lesson 11-3

ACTIVITY

A probability distribution is a function that gives the probability of each outcome in a sample space. You can use a frequency table or a graph to show a probability distribution.

The theoretical probability of rolling each number on a standard number cube is the same: 1 6 . 1 sixth , .  It is a uniform distribution, a probability distribution that is equal for each event in the sample space. Here is a table and graph of its probability distribution.

Now, suppose you roll two standard number cubes. You can show the probability distribution for the sum of the numbers by making a frequency table and drawing a graph.

Activity 1

Roll a pair of standard number cubes 36 times. Record the sum of the number cubes for each roll.

1. Copy the frequency table below. Use your data to complete your table.

   Event: Sum	2	3	4	5	6	7	8	9	10	11	12
   Frequency	□ white square	□ white square	□ white square	□ white square	□ white square	□ white square	□ white square	□ white square	□ white square	□ white square	□ white square
   Probability	□ white square	□ white square	□ white square	□ white square	□ white square	□ white square	□ white square	□ white square	□ white square	□ white square	□ white square

2. Copy and complete the graph below using your data.
3. Which sums did you expect to occur most often? Explain.
4. Make a graph of the probability distribution for the sums of two number cubes rolled 36 times, based on the theoretical probabilities of each sum.

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