Probability plays a major role in the medical community. Diagnoses are based on probabilities. They are really questions or "what if's", and are answered by theprobabilitythat the treatment will be the best for the ailment.

Let's look at probability in terms of both the real world and the medical community.

1. Survey 30 people to find out if they are left-handed or right-handed, and use the following chart to create a contingency table with the information.

Left-handed Right-handed Total Female Male Total

1. Answer the following questions about the information in your contingency table:
2. If a person is randomly selected from the survey participants, what is the probability that the person will be left-handed?
3. If you randomly choose a female from the people you surveyed, what is the probability that she is left-handed?
4. What is the odds ratio of choosing a left-handedfemale?
5. What is the relative risk of choosing a left-handedfemale?

Example

Green

Blue

Total

Cats

40 (A)

20 (B)

60 (A+B)

Dogs

30 (C)

40 (D)

70 (C+D)

Total

70 (A+C)

60 (B+D)

130 (A+B+C+D)

1. Probability of Green - (A+C)/(A+B+C+D): 70/130 = 0.54
2. Probability of Green Cat - A/(A+B): 40/60 = 0.67
3. Odds Ratio of Green Cat - (A/B)/(C/D) or AD/BC: (4040)/(2030) = 1600/600 = 2.67
4. Relative Risk of Green Cat - [A/(A+C)]/[B/(B+D)]: (40/70)/(20/60) = 1.71