Week 4 Discussion: Probability

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 the probability that 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.

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

Female Male Total

Answer the following questions about the information in your contingency table:

If you randomly choose afemale from the people you surveyed, what is the probability that she is left-handed?

What is the odds ratio of choosing a left-handed female?

Example

Total

Cats

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)

Probability of Green – (A+C)/(A+B+C+D): 70/130 = 54%

Probability of Green Cat – A/(A+B): 40/60 = 67%

Odds Ratio of Green Cat – (A/B)/(C/D) or AD/BC: (40*40)/(20*30) = 1600/600 = 2.67%

Relative Risk of Green Cat – [A/(A+C)]/[B/(B+D)]: (40/70)/(20/60) = 17.14%

Skim through at least one of the following articles on left-handed vs. right-handed people from the Chamberlain Library. Answer the following question: How do the probabilities and percentages for your study compare to those in the study you read?