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# Probability help watch

1. I've been sat here for an hour now trying to make sense of these questions, but I really don't have a clue. A bit of help would be much appreciated right now
2. (Original post by TwiMaster)

I've been sat here for an hour now trying to make sense of these questions, but I really don't have a clue. A bit of help would be much appreciated right now
What's causing the problem? Is it the notation for the set/event definitions?
3. (Original post by ghostwalker)
What's causing the problem? Is it the notation for the set/event definitions?
No, I'm okay with understanding the sets in this case. I just can't get my head around the questions
4. Guys, how would I answer parts a.) and b.) ?
5. (Original post by TwiMaster)

I've been sat here for an hour now trying to make sense of these questions, but I really don't have a clue. A bit of help would be much appreciated right now
Writing the sets in a simpler way may help:

A = {female residents}
B = {non-smoking residents}
C = {non-over weight residents}

Now what does A ∩ B ∩ C mean?
6. (Original post by notnek)
Writing the sets in a simpler way may help:

A = {female residents}
B = {non-smoking residents}
C = {non-over weight residents}

Now what does A ∩ B ∩ C mean?
Female residents who are non-smoking and are not overweight
7. (Original post by TwiMaster)
Female residents who are non-smoking and are not overweight
Correct. So how can that set be equal to the set of female residents?
8. (Original post by notnek)
Correct. So how can that set be equal to the set of female residents?
I still don't get how they could be equal to one-another
9. (Original post by TwiMaster)
I still don't get how they could be equal to one-another
Here's an example:

A = {a, b, c}
B = {a, b, c, d}
C = {a, b, c, d, e}

A ∩ B ∩ C = {a, b, c} = A

Let me know if you don't understand this example.

Think about what had to happen in this question for A ∩ B ∩ C to be equal to A. Then try to apply this idea to your question.
10. (Original post by notnek)
Here's an example:

A = {a, b, c}
B = {a, b, c, d}
C = {a, b, c, d, e}

A ∩ B ∩ C = {a, b, c} = A

Let me know if you don't understand this example.

Think about what had to happen in this question for A ∩ B ∩ C to be equal to A. Then try to apply this idea to your question.
From what I can see from your example, A is a subset of both B and C thus meaning that all the elements in A are also contained in B and C so A ∩ B ∩ C = A
11. (Original post by TwiMaster)
From what I can see from your example, A is a subset of both B and C thus meaning that all the elements in A are also contained in B and C so A ∩ B ∩ C = A
That's correct and this as it is may be OK as an answer.

But thinking about your specific question : what does this tell you about all the female residents?
12. (Original post by notnek)
That's correct and this as it is may be OK as an answer.

But thinking about your specific question : what does this tell you about all the female residents?
All the females are neither smokers or overweight?
13. (Original post by TwiMaster)
All the females are neither smokers or overweight?
Correct

Have another go at the next question and post your ideas if you are still stuck.
14. (Original post by notnek)
Correct

Have another go at the next question and post your ideas if you are still stuck.
Thank you! I definitely wouldn't have gotten that one

I think part b.) is implying that those who are overweight do not smoke
15. (Original post by TwiMaster)
Thank you! I definitely wouldn't have gotten that one

I think part b.) is implying that those who are overweight do not smoke
Correct again.

Is c) OK?
16. (Original post by notnek)
Correct again.

Is c) OK?
Yay, Is c.) saying that being male is independent of being a smoker?
17. Does anybody know how to answer part c.) ?
18. (Original post by TwiMaster)
Yay, Is c.) saying that being male is independent of being a smoker?
I presume you mean part d).

'Fraid not. And you want to be careful using the terms "independent" and similar, as they have a specific meaning in probability and statistics.

You've identified that one set represents male residents, and one represents non-smokers. What's the equality sign telling you?

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