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Leaving Cert '11/'12 Off-Topic 2

Eathrin

New thread fellow Leaving Certs!

2 months to go, things be getting serious now:cool:

Let's get some new epic tags going:pac:

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Meowth

Coeurdepirate wrote: »

Historykitten wrote: »

Sitting in study kill me now why did I opt for this

What time is your study from on what days? Mine is from 6-10 on weekdays and 10-4 on Saturdays. so depressing

Mondays I do 7 to 9 Tuesday and Wednesday till 6 Thursday 7 to 9 and Friday till half 5

meh hate it

wasn't a very productive study today either

half finished essay that is all over the place

Omg coeur that's so long

dunno how you do that

is Saturday study good? I think I should join it

finality

Wait now I think it could be 97%. Anyway, I think basically if you study 5 it's very unlikely you won't have at least 2, as all 3 of the ones you didn't study would have to come up.

Hmm. If you study ONE poet, you have a 50% chance of them coming up. Study two poets and you have a 79% chance one will come up. I probably shouldn't say that though....

PictureFrame wrote: »

How are you so good at Maths finality? Were you always good in like Primary School or whatever? I'd love an auld Mathsy brain.

I'm NOT good at probability to be honest. :L It's so confusing.
I have always liked maths, but I've only really loved it since 5th year. I think that's because in primary school and junior cert if I was finished the questions we were doing or whatever early, I'd end up waiting and though I know it sounds petty, I think that actually put me off the subject a little bit. The teacher I have for leaving cert is amazing, she let me work ahead and teach myself since almost the start of fifth year, so I ended up doing a LOAD of maths all the time because I genuinely found it fun, I'd do every question in the book until something made complete sense to me. Then I started getting between 95 and 100% in class tests whereas in junior cert I would've been getting high Bs/low As. Half way through fifth year I banned myself from doing maths after school. :L
I wish I were better at maths, I think I'd be lost if I studied pure maths in college.

So that's my maths life story. What about everyone else, how did you find maths all your lives? :P

Eathrin

Eathrin wrote: »

No method springs to mind. In Bernoulli trials I think the events have to be independent, that's where I first went wrong. I'm certain there's a way to do it regularly but I'm yet go figure that out.

8C4 gives 70 possible outcomes.
There are only 5 possible outcomes where only one studied poet comes up. I.e post 6 7 and 8 with each of the first 5 poets.
So 1-5/70 is 93%

Okay so this can be done if we multiply 5/8 x 3/7 x 2/6 x 1/5
Obviously order doesn't matter to us so we multiply this by 4.

Edit: Actually that doesn't sound right...it's definitely 93% though.
Anybody find a better quick method to arrive at this?

finality

Eathrin wrote: »

Okay so this can be done if we multiply 5/8 x 3/7 x 2/6 x 1/5
Obviously order doesn't matter to us so we multiply this by 4.

But surely because one poet coming up is definite, you can just leave that out entirely and treat it as if you've studied 4 out of 7, where 3 poets will come up. Oh god why so confusing.

edit: there are 35 possible ways of choosing 3 from 7. Only one of those will be all 3 you haven't studied.1 - 1/35 = 97%

if you do 1 - (3/7 x 2/6 x 1/5) this gives you the same thing.

My final answer is 97. Haha. At the end of the day it's between 93 and 98%. :L

Namlub

Studied all day but I feel like I haven't achieved anything. Also I timed myself writing a history essay, took me an hour. This exam is going to kill me.

Eathrin

finality wrote: »

But surely because one poet coming up is definite, you can just leave that out entirely and treat it as if you've studied 4 out of 7, where 3 poets will come up. Oh god why so confusing.

Yes but that's assuming you know who comes up.
So we multiply by 5 to cover all studied poets.
Still leaves me short, hmm

Meowth

Lads anybody else gonna be booking accomodation in UCD ?

cillian95

Hmmmm.. all these probabilities are way off from mine:

At least 2 poets coming up if you study 5:
2poets: 5/8 X 4/7 X 3/6 X 2/6 = 1/14
3poets: 5/8 X 4/7 X 3/6 X 3?5 = 3/28
4poets: 5/8 X 4/7 X 3/6 X 2/5 = 1/14
1/14 + 3/28 + 1/14 = 1/4 = 25%

I really can't see how 93% is right? Will someone please explain where I'm going wrong.. otherwise my maths teacher and I are going to have great fun figuring this out tomorrow

Con_Con93

The quickest and easiest way to do it is the way you had it done. 1 -P(0) - P(1).
i.e 1 - the probability of getting none - the probability of getting one.

That is 1 - 0 - 5/70.
giving 65/70. Which is 92.857%.

Canard

I am totally asking my maths teacher this tomorrow :L

Togepi

@Eathrin I have no idea what you're on about, but thanks. :P Like, why are you using 8C4 and then why do you put 5 over it?

And @Finality, I would've thought doing one poet leaves you with a 25% chance of them coming up, then I thought about and the 50% makes sense.

How did you get 79% for two poets though? I keep getting 75% or 100%? :pac:

cillian95

finality wrote: »

But surely because one poet coming up is definite, you can just leave that out entirely and treat it as if you've studied 4 out of 7, where 3 poets will come up. Oh god why so confusing.

edit: there are 35 possible ways of choosing 3 from 7. Only one of those will be all 3 you haven't studied.1 - 1/35 = 97%

if you do 1 - (3/7 x 2/6 x 1/5) this gives you the same thing.

My final answer is 97. Haha. At the end of the day it's between 93 and 98%. :L

That's not right, five of them will include the three poets you didn't study. These are the five cases where only one of the ones you studied come up.

By the way, I'm totally the same as you with maths. I've just officially banned myself from doing maths for the next month: I just love it and every time I go to study I end up doing hours and hours of maths. Funniest thing is that I just found out I'm pretty decent at maths this year : got a C in my junior and I'm looking for an A1 in June

kitty9

made in chelsea is on

die spencer

kitty9

omg die spencer

Eathrin

Togepi wrote: »

@Eathrin I have no idea what you're on about, but thanks. :P Like, why are you using 8C4 and then why do you put 5 over it?

And @Finality, I would've thought doing one poet leaves you with a 25% chance of them coming up, then I thought about and the 50% makes sense. How did you get 79% for two poets though? I keep getting 75% or 100%? :pac:

It's definitely 93%
The three poets you haven't studied will appear in 5 possible cases, each time with one of the poets you have studied.
So 65/70 times you will have a choice.

finality

Eathrin wrote: »

Yes but that's assuming you know who comes up.
So we multiply by 5 to cover all studied poets.
Still leaves me short, hmm

But it's not, it's assuming all the poets you've studied are essentially the same and it doesn't matter which comes up. I think?

Con_Con93

The easiest way to look at it is:
1 = P(0) + P(1) + P(2) + P(3) + P(4).
We want the probability of at least 2. Which is equivalent to P(2) + P(3) + P(4).
Therefore we want 1 - P(0) - P(1).

Eathrin

cillian95 wrote: »

Hmmmm.. all these probabilities are way off from mine:

At least 2 poets coming up if you study 5:
2poets: 5/8 X 4/7 X 3/6 X 2/6 = 1/14
3poets: 5/8 X 4/7 X 3/6 X 3?5 = 3/28
4poets: 5/8 X 4/7 X 3/6 X 2/5 = 1/14
1/14 + 3/28 + 1/14 = 1/4 = 25%

I really can't see how 93% is right? Will someone please explain where I'm going wrong.. otherwise my maths teacher and I are going to have great fun figuring this out tomorrow

You are assuming order comes into play.
If you multiply your top result by 6 and your 2nd result by 4 you get your answer to be 13/14 which is correct.

Meowth

Togepi wrote: »

Can any mathsy person work out the probability of having at least 2 of your poets come up on the day if you study 5?

I tried it and I got 93%, surely that's way off?!

The question that's gonna keep every LC up tonight :P
Lads I really don't know why ye care so much about what % chance you've got of 2 coming up if you learn five :rolleyes: Like you have fairly good chance that 2 will come up and you'll defo have at least one you've studied coming up

Togepi

Eathrin wrote: »

It's definitely 93%
The three poets you haven't studied will appear in 5 possible cases, each time with one of the poets you have studied.
So 65/70 times you will have a choice.

Ahh that kind of makes sense! I was wondering why you said it was 5 cases rather than one. Never would've thought of putting it over 70 though.

Thanks.

@HistoryKitten I know, sorry everyone! :P I care though 'cause four of my poets are the least likely to come up, but I really want one of them to come up.

Edit: And I also care 'cause I'd like to have a choice incase one of the questions is horrible! :P Plus I don't want to answer on Plath 'cause I don't know her well enough and there'll be loads answering on her so it'll be harder to do well.

Eathrin

finality wrote: »

But it's not, it's assuming all the poets you've studied are essentially the same and it doesn't matter which comes up. I think?

But it does matter who comes up.
It affects the other results. Therefore we can't say anybody is definitely going to come up.
It must be 4 x 5/8 x 3/7 x 2/6 x 1/5
We multiply by 4 because order does not matter ( and in this instance it doesn't matter who comes up so we don't multiply by 24)

finality

Con_Con93 wrote: »

The easiest way to look at it is:
1 = P(0) + P(1) + P(2) + P(3) + P(4).
We want the probability of at least 2. Which is equivalent to P(2) + P(3) + P(4).
Therefore we want 1 - P(0) - P(1).

Doesn't that give 98%?

Oh god. I hate probability.

cillian95

Eathrin wrote: »

You are assuming order comes into play.
If you multiply your top result by 6 and your 2nd result by 4 you get your answer to be 13/14 which is correct.

Ah! Thanks! Couldn't see where i was going wrong. Jesus, never should have said I was hoping for an A1 :L

So studying one poet means you've got a 50/50 chance of them coming up aye? Anyone else crazy enough to take the risk with me

..?

Togepi

The ironic part is that probability is my favourite section of the entire maths course.

Mysteriouschic

I'm only studying Plath, Rich , Heaney and Kavanagh. We did have Boland done but I don't think there's point on me going over her. Would these four poets be enough? or should I try one more poet other than Boland as she's probably unlikely to come up or am I better off focusing on these four?

Togepi

Technically if you only do four there is a chance you won't have any poet on the day. :P But that chance is really small, so it's up to you!

Wesc.

Mysteriouschic wrote: »

I'm only studying Plath, Rich , Heaney and Kavanagh. We did have Boland done but I don't think there's point on me going over her. Would these four poets be enough? or should I try one more poet other than Boland as she's probably unlikely to come up or am I better off focusing on these four?

Ask Eathrin

Eathrin

Okay here's a really interesting stat I've just worked out.

First of all who are the three least likely poets to appear on our exam?
Frost, Boland, Kavanagh most would say. Assume the probability of any two of these appearing is 0.
Now if you're a person who likes to analyse trends this applies to you. If you study 2 poets the chances of 1 of them appearing is 93%. Not bad huh?
That's what I'm going with anyway.

finality

Eathrin wrote: »

But it does matter who comes up.
It affects the other results. Therefore we can't say anybody is definitely going to come up.
It must be 4 x 5/8 x 3/7 x 2/6 x 1/5
We multiply by 4 because order does not matter ( and in this instance it doesn't matter who comes up so we don't multiply by 24)

What I was doing was taking one poet out of the equation completely. Because one definitely has to come up, wouldn't it be irrelevant which it is, as they're then just gone from all future calculations? I don't know if I'll be able to get my head around this :L

Namlub

They might be absolute snakes and put Boland on just because she seems so unlikely. But honestly I can't see Plath and/or Heaney not coming up so I'm going to spend way more time on them than Boland (doing Rich and Kavanagh as well)