we were given a chart - "researchers developed the following tabel of joint probabilities of number of drinks per day and development of ulcers"
and the question is
a. what proportion of people have ulcers - how am i supposed to know htis
b. what is the prob that someone who does not drink alcohol develops an ulcer
c. what is the prob that someone who has an ulcer does not drink alcohol
d. what is the probability that someone who does not have an ulcer consumes two alcoholic drinks per day?
how are b and c different
here's the chart.
drinks.............ulcer............no ulcer
none..............1%...............22%
one.............3%.............(19%)
two..............3%............(32%)
more than two 4%................16%
assume 100 folks. Those numbers as percents are now real humans.
Pr(ulcers)=(1+3+3+4)/100
Pr(ulcer:no drink)=1/(22+1)
pr(no drink:ulcer)=1/(1+3+3+4)
Pr(two drinks: no ulcer)=32/(22+19+32+16)
check me.