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# S1 Watch

1. I can't get my head around probabilities.

What should I do?
2. (Original post by zed963)
I can't get my head around probabilities.

What should I do?
What in particular can't you get your head around? Surely you understand the basic idea, that if you're uncertain about something then you assign probabilities to the various outcomes?
3. (Original post by Smaug123)
What in particular can't you get your head around? Surely you understand the basic idea, that if you're uncertain about something then you assign probabilities to the various outcomes?
It's like knowing when to apply which formula and how to solve the questions.
4. (Original post by zed963)
It's like knowing when to apply which formula and how to solve the questions.
What sort of question? Can you give me an example?
In general, I don't bother with knowing what to do when - I just do the obvious thing with each question. I suspect that's among the least helpful advice you've ever had, but without knowing specific types of question you don't know where to start on, I can't do much better.
5. (Original post by Smaug123)
What sort of question? Can you give me an example?
In general, I don't bother with knowing what to do when - I just do the obvious thing with each question. I suspect that's among the least helpful advice you've ever had, but without knowing specific types of question you don't know where to start on, I can't do much better.
http://www.thestudentroom.co.uk/show....php?t=2644742

This one.
6. There are two key tools in probability - the Venn diagram and the tree diagram. I still use tree diagrams all the time at university level. Was the Venn diagram your first thought on seeing that question?
7. (Original post by Smaug123)
There are two key tools in probability - the Venn diagram and the tree diagram. I still use tree diagrams all the time at university level. Was the Venn diagram your first thought on seeing that question?
It was a probability tree that I first thought of, but I was suggested to make a venn diagram and so I did, I think it's the last post of that thread.
8. (Original post by zed963)
It was a probability tree that I first thought of, but I was suggested to make a venn diagram and so I did, I think it's the last post of that thread.
The best rule of thumb I can think of is "Always make a tree diagram first in probability questions, and if that doesn't work, make a Venn diagram".
9. (Original post by Smaug123)
The best rule of thumb I can think of is "Always make a tree diagram first in probability questions, and if that doesn't work, make a Venn diagram".
I've drawn one in the other thread. Can you have a look please ?
10. (Original post by zed963)
I've drawn one in the other thread. Can you have a look please ?
What you know is that the total of *everyone in the Breakfast pod* comes to 2/3, and 9/25 *of the people in the Breakfast pod* are in the Both pod. Your picture says that 9/25 of *everyone* are in the Both pod, not that 9/25 of *the people in Breakfast*. Was that just a slip of the pen (or carelessness), or do you understand why your diagram isn't right?

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Updated: April 16, 2014
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