Bad gums may mean a bad heart. Researchers discovered that 80% of people who hav

Question

Bad gums may mean a bad heart. Researchers discovered that 80% of people who have suffered a heart attack had periodontal disease, an inflammation of the gums. Only 30% of healthy people have this disease. Suppose that in a certain community heart attacks are quite rare, occurring with only 12% probability.

A. If someone has periodontal disease, what is the probability that he or she will have a heart attack?

Probability =

B. If 39% of the people in a community will have a heart attack, what is the probability that a person with periodontal disease will have a heart attack?

Probability =

Explanation / Answer

Solution:

G = gum (periodontal) disease

H = heart attack

qA

P(G & H) = 80% * 12% = 8% = A

P(G & H') = 31% * 90% =27.9%

P(G) = sum of the above = 35.9% = B

P(H | G) = A/B

= 0.2228

qB
do exactly as above with different figures for P(H)

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