This page features some practice questions regarding probability rules. The questions are provided below, and the answers are provided further below. Please contact me at MHoward@SouthAlabama.edu if you have any questions or comments.

**Questions**

1.) An event has a 25% chance of occurring. What is the chance of it not occurring? What rule did you use to determine this?

2.) Event A has a 50% chance of occurring, and Event B has a 50% chance of occurring. What is the probability that Event A or Event B occurs, assuming that they are NOT mutually exclusive? What rule did you use to determine this?

3.) Event A has a 50% chance of occurring, and Event B has a 50% chance of occurring. What is the probability that Event A and Event B occurs, assuming that the events are independent? What rule did you use to determine this?

4.) 2.) Event A has a 50% chance of occurring, and Event B has a 50% chance of occurring. What is the probability that Event A or Event B occurs, assuming that they are mutually exclusive? What rule did you use to determine this?

5.) An event has a 5% chance of occurring. What is the chance of it not occurring? What rule did you use to determine this?

6.) Event A has a 10% chance of occurring, and Event B has a 10% chance of occurring. What is the probability that Event A and Event B occurs, assuming that the events are independent? What rule did you use to determine this?

7.) An event has a 80% chance of occurring. What is the chance of it not occurring? What rule did you use to determine this?

8.) Event A has a 60% chance of occurring, and Event B has a 60% chance of occurring. What is the probability that Event A and Event B occurs, assuming that the events are independent? What rule did you use to determine this?

9.) Event A has a 20% chance of occurring, and Event B has a 20% chance of occurring. What is the probability that Event A or Event B occurs, assuming that they are NOT mutually exclusive? What rule did you use to determine this?

10.) Event A has a 20% chance of occurring, and Event B has a 20% chance of occurring. What is the probability that Event A or Event B occurs, assuming that they are mutually exclusive? What rule did you use to determine this?

Answers

1.) 75% – Complement Rule

2.) 75% – Addition Rule

3.) 25% – Multiplication Rule

4.) 100% – Addition Rule

5.) 95% – Complement Rule

6.) 1% – Multiplication Rule

7.) 20% – Complement Rule

8.) 36% – Multiplication Rule

9.) 36% – Addition Rule

10.) 40% – Addition Rule