20% of people had a heart attack, 16% of people are current smokers and 12 % of

Question

20% of people had a heart attack, 16% of people are current smokers and 12 % of people had a heart attack while smoking. Let A be the event who are current smoker and B be the event who had a heart attack

1.Calculate P(A), P(B), P(A and B) and P(not A and B)

2. If a person is randomly selected from current smoker. What is the probabilty of this person had a heart attack.

3.If a person is randomly selected from current nonsmoker. What is the probabilty of this person had a heart attack

4. What is risk of having a heart attack for current smoker.What is risk of having a heart attack for current nonsmoker.

5. What is relative risk of having heart attack for current smoker compared to current non smoker.

6. What is odds of having heart attack among those who are current smoker and odds of having heart attack among those who are current non smoker

7. What is odds ratio of having a heart attack for current smokers compared to current non smoker

Explanation / Answer

Ans: 1.P(A)=0.16,P(B)=0.2,

P(A and B)=0.12,

P(not A and B)=P(B)-P(A and B)

=0.2-0.12=0.08

2.P(B/A)=P(A and B)/P(A)=0.12/0.16=0.75

3. P(B/ not A)=P(not A and B)/P(not A)=0.08/0.84=0.095

4.Risk of having heart attack from current smoker=0.75

Risk of having heart attack from current nonsmoker=0.095

5. Relative risk=( 0.75-0.095)/0.095

6. odds of having heart attack among those who are current smoker =0.12=7.33/1

odds of having heart attack among those who are current non smoker=0.08=11.5/1

7.odds ratio of having a heart attack for current smokers compared to current non smoker=0.12/0.08=1.5/1

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