If I am interpreting you table correctly, the probability of being a man (M) is 528/991 (total men dividing by the grand total) and the probability of being a heavy smoker (HS) is total HS divided by the grand total. The probability of either one event or another occurring is found by adding the probability of the individual events.
I hope this helps. Thanks for asking.
The table below shows the smoking habits of a group of asthma sufferers
NS OS RS HS T
M 358 32 90 48 528
W 307 35 77 44 463
T 665 67 167 92 991
If one of the 991 people is randomly selected, find the probability that the person is a man or a heavy smpker
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