# Random Probability

• Aug 2nd 2009, 06:46 PM
mathmagic
Random Probability
Hi! This problem is giving me trouble because the wording in the question is confusing. Please help...

In a British study around 1950, a group of 649 men with lung cancer were surveyed. A control group of the same size was established from a set of men who did not have lung cancer. The groups were matched according to ethnicity, age, and socioeconomic status. The statistics from the survey follow:

[B]If one person is chosen at random from each of the two groups (smokers and nonsmokers), what is the probability that each person chosen has cancer?

Lung Cancer Cases Controls Totals
Smokers 647=lung cancer 622=controls 1269=totals

Nonsmokers 2=lung cancer 27=controls 29=totals

Thanks!
[/CENTER]
• Aug 2nd 2009, 08:52 PM
mr fantastic
Quote:

Originally Posted by mathmagic
Hi! This problem is giving me trouble because the wording in the question is confusing. Please help...

In a British study around 1950, a group of 649 men with lung cancer were surveyed. A control group of the same size was established from a set of men who did not have lung cancer. The groups were matched according to ethnicity, age, and socioeconomic status. The statistics from the survey follow:

[b]If one person is chosen at random from each of the two groups (smokers and nonsmokers), what is the probability that each person chosen has cancer?

Lung Cancer Cases Controls Totals
Smokers 647=lung cancer 622=controls 1269=totals

Nonsmokers 2=lung cancer 27=controls 29=totals

Thanks!

[/center]

It looks to me like (647/1269).(2/27) = ....
• Aug 2nd 2009, 09:08 PM
mathmagic
Random Probability
Hi! Thank you very much for your response. I just had one question...Why is the random probability for the nonsmokers 2/27 instead of 2/29 since the random probability for smokers is 647/1269?
• Aug 3rd 2009, 03:39 AM
mr fantastic
Quote:

Originally Posted by mathmagic
Hi! Thank you very much for your response. I just had one question...Why is the random probability for the nonsmokers 2/27 instead of 2/29 since the random probability for smokers is 647/1269?

Surely the answer is obvious .....