1. Sec. 3.5: Contingency Tables A contingency table is a way of organizing data to make finding conditional probabilities easier.

2. Example 1: Speeding violations and cell phone users Speeding violation in last year No speeding violation in last year Total Cell phone user 25280305 Not a cell phone user 45405450 Total70685755 Find the following probabilities: P(person uses a cell phone) P(person had no violations last year) P(person had no violations last year and uses a cell phone) P(person had a violation given they use a cell phone) P(person had no violation given they do not use a cell phone)

3. Example 2: The following table shows a random sampling of 100 hikers and their preferred hiking area SexCoastLakesMount ains Total Female181645 Male1455 Total41

4. Practice #1: A medical trial into the effectiveness of a new medication was carried out. 120 females and 90 males took part in the trial. Out of those people, 50 females and 30 males responded positively to the medication. Given below is a contingency table with the given information filled in. FemaleMaleTotals Positive5030 Negative Totals12090

5. Practice #2: Use the given contingency table to answer the following questions Brown Eyes Not Brown Eyes Totals Black Hair5030 Red Hair7080 Totals What is the probability that someone with black hair has brown eyes? What is the probability that someone has black hair? What is the probability that someone has brown eyes? Are having black hair and having brown eyes dependent or independent events?