1. 4.3 Introduction to Probability
Objective: Find the experimental probability that an event will occur.
Standards Addressed: D: Compare and contrast results from observations and mathematical models E: Make valid inferences, predictions and arguments based on probability.

2. The probability of an event is the likelihood that the event will occur. Probability is measured on a scale from 0% to 100%, or from 0 to 1.

3. Two Probability Experiments
Part I:
Roll a pair of # cubes 20 times and record the # of times that a sum of 7 occurs.
Compare your results with the results of other groups in your class.
Find a percent for the entire class by dividing the total number of sums of 7 that occurred by the total number of rolls for the whole class.
Are your group and class results what you expected? Explain.

4. Part II:
Toss a coin 20 times and record how many times it comes up heads. Divide this number by 20 to find the percent of heads that occurred.
Compare your results with the results of other groups in your class.
Find a percent for the entire class by dividing the total number of heads that came up by the total number of tosses for the whole class.
Are your group and class results what you expected? Explain.

5. A probability experiment consists of a number of trials.
For any given trial, the result, or outcome, may or may not be favorable.
If you are interested in the probability that a tossed coin comes up heads, then heads is a favorable outcome.

7. Ex. 1a.

8. Ex. 1 b. Two number cubes were rolled 100 times
Ex. 1 b. Two number cubes were rolled 100 times. A sum greater than 8 appeared 29 times. Based on this experiment, what is the experimental probability that two rolled number cubes will show a sum greater 8?
29/100
29%

9. Ex. 1c. Two number cubes were rolled 200 times
Ex. 1c. Two number cubes were rolled 200 times. A number greater than 9 appeared as a sum 28 times. Based on this experiment, what is the experimental probability that two number cubes will show a sum that is greater than 9 when rolled?
28/200
.14 = 14%

10. Ex. 2a.

11. Ex. 2b. Two coins were tossed 200 times. Two tails appeared 52 times
Ex. 2b. Two coins were tossed 200 times. Two tails appeared 52 times. Based on this experiment, what is the experimental probability of two flipped coins showing two tails?
52/200
.26 = 26%

12. Ex. 2c. Two coins were tossed 100 times. Two tails appeared 19 times
Ex. 2c. Two coins were tossed 100 times. Two tails appeared 19 times. Based on this experiment, what is the experimental probability that two tails will appear when these coins are tossed again?
19/100
.19 = 19%