stats between a relation

orendacl

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Nov 10, 2010
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The relationship between high blood pressure and cigarettes - data is as follows:
Non-smokers moderate heavy total
High blood pressure 21 36 30 87
normal blood press. 48 26 19 93
totals 69 62 49 180


If you randomly pick one of the test subjects, what is prob. that:
a- they have high blood pressure
b - they are non smokers
c - they are a non smoker who happens to have high blood pressure
d - they have high blood pressure and (given) are a heavy smoker
e - they are a non smoker, (given) ther person is experiencing high blood pressure symptoms

So, here is what I cannot understand in the problem:
I recall reading that the probability of an event is the number of ways an event can occur, divided by the number of all possible outcomes.
So, example: Say you have 5 marbles in a container, 2 reds, 3 greens, what is the probability of selecting a red marble at random?
Well, that is 2/5, since there are 2 ways you can get a red marble (select either of the 2 red marbles) then divide by the total number of possible outcomes (there are a total of 5 marbles to choose from).

So here we are given a number of people (is this the possible outcomes?) and we want to find the probability of "some event" (I think that is the subject have high blood pressure, are non-smokers, and are nonsmokers who have high blood pressure, respectively -right?)

How do you proceed?
 
You may be talking yourself out of things that are relatively obvious. Given that lovely grid of results, just read off the answers.

\(\displaystyle \begin{array}{lcccc} & Non-smokers & moderate & heavy & total
\\ High\;blood\;pressure & 21 & 36 & 30 & 87 \\ normal\;blood\;press & 48 & 26 & 19 & 93 \\ totals & 69 & 62 & 49 & 180 \end{array}\)

If you randomly pick one of the test subjects, what is prob. that:
a- they have high blood pressure 87/180
b - they are non smokers 69/180
c - they are a non smoker who happens to have high blood pressure 21/180
d - they have high blood pressure and (given) are a heavy smoker 30/49
e - they are a non smoker, (given) ther person is experiencing high blood pressure symptoms 21/87
 
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