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S1 Probability, god help me watch

1. So I'm reviewing Chapter 5 of S1 today. It's definitely and inarguably the hardest chapter of the whole book. The tree diagrams are fairly easy, but those ridic dashes and signs in the P(A) and that sort of business are getting me really confused. It tells you what they mean but make absolutely no sense when read out in your head

Does anyone have any advice on how to read them, or just general advice on this poorly written chapter - perhaps a website? Usually Edexcel explains things well; C1 was the most aesthetically pleasing thing to read. But Ch5 of S1 is making me want to smash my head on the desk. Thank you
2. AnB should be read "A and B"

AuB should be read "A or B" and should be thought of as "A, B or A and B"

A' often means not A (so if A = it will rain, A' = it will not rain)

Draw a Venn diagram whenever you can - you might think the question is trivial/you know what it's talking about/you're "above" doing diagrams because they're made for idiots, but no, you should draw them and use them.

The only way to get used to the notation is to start from the most trivial exercises and work your way up doing every single question in the chapter.
3. AuB more than the rest confuses me; I hate the idea of one notation or the other, it messes up my logic. Why can't I understand this

I've tried working my way up, doesn't work, can't grasp the signs.
4. Swayum has explained it well
drawing venn diagrams will help a lot since the follow up questions will be straightforward.
P(AIB)= intersection of A and B divided the P(B)

ps: i also dislike this chaper but in the past papers, some are way easy than others, and normal distribution dont let me get started on how badly the edexcel book explains it
5. (Original post by snow leopard)
AuB more than the rest confuses me; I hate the idea of one notation or the other, it messes up my logic. Why can't I understand this

I've tried working my way up, doesn't work, can't grasp the signs.
Draw a Venn diagram. AuB represents everything in the circles! Everything shaded in blue below is AuB:

If I ask you "do you have any food or water?", when will you say yes? Let's say A = having food, B = having water.

When will you answer yes to my question?

1) You'll answer yes if you have food but not water. This represents A in the circle but not the intersection (so just the bit on the left)

2) You'll also answer yes if you have water but no food. This represents B in the circle but not the intersection.

3) Crucially, you'll also answer yes if you have both food and water! Go try it on someone in your family, give them food and water and then ask them "do you have any food or water?" and they will reply yes. AuB includes this possibility, which is the intersection of A and B (shaded blue in the diagram in the middle).

Hence AuB is everything in the circles (everything shaded blue), but not the stuff outside the circles (shaded white).
6. (Original post by Swayum)
Draw a Venn diagram. AuB represents everything in the circles! Everything shaded in blue below is AuB:

If I ask you "do you have any food or water?", when will you say yes? Let's say A = having food, B = having water.

When will you answer yes to my question?

1) You'll answer yes if you have food but not water. This represents A in the circle but not the intersection (so just the bit on the left)

2) You'll also answer yes if you have water but no food. This represents B in the circle but not the intersection.

3) Crucially, you'll also answer yes if you have both food and water! Go try it on someone in your family, give them food and water and then ask them "do you have any food or water?" and they will reply yes. AuB includes this possibility, which is the intersection of A and B (shaded blue in the diagram in the middle).

Hence AuB is everything in the circles, but not the stuff outside the circles.
+REP. Nice explanation.
7. Yeah, chapter 5 is really the hardest chapter, but as Swayum said, diagrams make everything a lot easier. Chapter 5 shows what AUB and ANB represent so I think his explanation was a little unnecessary if you took 5 minutes to look at the book.
8. (Original post by Swayum)
Draw a Venn diagram. AuB represents everything in the circles! Everything shaded in blue below is AuB:

If I ask you "do you have any food or water?", when will you say yes? Let's say A = having food, B = having water.

When will you answer yes to my question?

1) You'll answer yes if you have food but not water. This represents A in the circle but not the intersection (so just the bit on the left)

2) You'll also answer yes if you have water but no food. This represents B in the circle but not the intersection.

3) Crucially, you'll also answer yes if you have both food and water! Go try it on someone in your family, give them food and water and then ask them "do you have any food or water?" and they will reply yes. AuB includes this possibility, which is the intersection of A and B (shaded blue in the diagram in the middle).

Hence AuB is everything in the circles (everything shaded blue), but not the stuff outside the circles (shaded white).
LOL FUN ANALOGY. I GET IT - SO EVERYTHING INSIDE THE CIRCLES. reps+
9. (Original post by Extricated)
Yeah, chapter 5 is really the hardest chapter, but as Swayum said, diagrams make everything a lot easier. Chapter 5 shows what AUB and ANB represent so I think his explanation was a little unnecessary if you took 5 minutes to look at the book.
To hell with the book, its rubbish, its designed to fail people and pass only people with tutors/private shcool teachers to explain it. It doesn't talk of possibilities in its explanations, its very vague, I know understand it from that term 'possibilities' by the user with the analogy. It could be x y or z in any combination. The book says zilch in terms of comprehendable english imo.

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