****Leaving Certificate: Higher Level Maths Discussion****

plmko

PaleMoonlight wrote: »

Anyone know if we need to be able to prove the twin rule?

I'm unsure about this too. But I learned it anyway. It's very simple and you can get most of your ideas from the log tables just replace r! With (n-r)! In the formula on the logs.

plmko

Calvin Leong wrote: »

Any predictions for the theorems/constructions? Or even just the most important :rolleyes:

12 or 13?

PaleMoonlight

MegGustaa wrote: »

What is that? Never heard of it..

It's from probability. It states that nCr = nCn-r. For example 6C4 = 6C2

plmko wrote: »

I'm unsure about this too. But I learned it anyway. It's very simple and you can get most of your ideas from the log tables just replace r! With (n-r)! In the formula on the logs.

Yeah I think I'll learn it just to be safe

plmko

Must go through all my papers now to make sure I haven't missed anything!

aleatorio

plmko wrote: »

Sample size is 10
[used 400 in my pre and got it wrong!]

MegGustaa wrote: »

Yep, sample size n = 10, and you use the standard deviation of the means (found by dividing the SD by root n).

The expected mean of all the smaller sample is also 200, by the CLT

Thanks!

aleatorio

PaleMoonlight wrote: »

It's from probability. It states that nCr = nCn-r. For example 6C4 = 6C2



Yeah I think I'll learn it just to be safe

Care to elaborate? How would you prove it? Its not in my book

TheBegotten

If I remember correctly, the formula for nCr is n!/(r!(n-r)!) which is in the log tables, so to prove it I presume you use a complex proof by induction. Either that or sub in (n-r) for n and see where that leaves you.

PaleMoonlight

aleatorio wrote: »

Care to elaborate? How would you prove it? Its not in my book

To Prove: nCr = nC(n-r)

LHS = nCr= n!/r!(n-r)! (This is in the log books apparently but I can't find the page at the moment)

RHS = nC(n-r) = n!/(n-r)!(n-(n-r))!
= n!/(n-r)(n-n-r)!
= n!/(n-r)!(r)!
therefore RHS = LHS

Carcar123

aleatorio wrote: »

This is from the Examcraft mock and I think it's the Central Limit theory?

'400 samples of size 10 are taken from a production line producing jars of gravy. The mean weight of a jar is 200g with a standard deviation of 1.5g. Calculate the limits between which you would expect 95% of the sample mean to lie'

I know the formula for the mean of the sample is the SD divided by the sample size, but is the sample size 10 or 400(10)?

And then it would just be 200+/- 2 standard deviations.. Yeah....?

What would be the answer to this then?

plmko

I'd really appreciate it if anyone could help me with this. It corresponds with page 85 of our sample papers, that being Sample 2 P2.

How do you do part (b) and part (c)?

PLEASE HELP URGENT

Carcar123 wrote: »

What would be the answer to this then?

Between 199.05g and 200.95g

romanita

Does anyone know if you can use the area of a triangle - 1/2absinC - to derive the sine rule.? If they don't specify how they want you to do it that is..

eefah

How many marks would like, using a calculator to get the correlation co-efficient, or the standard deviation be worth? Realistically, I'm not gonna be able to learn that at this stage ....

jellytots95

Does anyone have any pearls of wisdom tonight? There were great tips here for paper1! :P

PaleMoonlight

romanita wrote: »

Does anyone know if you can use the area of a triangle - 1/2absinC - to derive the sine rule.? If they don't specify how they want you to do it that is..

That's how my teacher taught it, and it came up last year as; "Using a formula for the area of a triangle, or otherwise [prove sine rule]".

TheBegotten

eefah wrote: »

How many marks would like, using a calculator to get the correlation co-efficient, or the standard deviation be worth? Realistically, I'm not gonna be able to learn that at this stage ....

We were never shown how to get it otherwise...base it off the amount of space they give you. If it's only a small box or line they're not looking for calculations.

eefah

TheBegotten wrote: »

We were never shown how to get it otherwise...base it off the amount of space they give you. If it's only a small box or line they're not looking for calculations.

Well yeah my point is that if I'm asked to get the correlation co-efficient, I'm just gonna have to guess :P
I guess i'm just hoping it wont be worth more than 5 marks if it does come up.

miissjuly

I learnt more on boards than in class.

eefah

miissjuly wrote: »

I learnt more on boards than in class.

I learned more listening to people on youtube explain things in soothing voices than I did in class.
.... which was a method recommended to me on boards so yeah, same.

Shane15

Anyone know a good video that explains theorems 12 and/or 13?

eefah

Shane15 wrote: »

Anyone know a good video that explains theorems 12 and/or 13?

Nah but there's powerpoints for them on the project maths website: projectmaths.ie/students/cd-strand1and2/strand2-geoandtrig.asp

They're ones under 'proofs,' if you click the link they download automatically.

Shane15

eefah wrote: »

Nah but there's powerpoints for them on the project maths website: projectmaths.ie/students/cd-strand1and2/strand2-geoandtrig.asp

They're ones under 'proofs,' if you click the link they download automatically.

Great, thanks.

Tesco TripleChicken

eefah wrote: »

How many marks would like, using a calculator to get the correlation co-efficient, or the standard deviation be worth? Realistically, I'm not gonna be able to learn that at this stage ....

takes 5 mins to learn both just look it up and practice with a few problems

conor1508

Videos on theorems 11,12,13 are available on this YouTube channel: "oconailldc's"

Jones82

Oh ****, do we have to know the trigonometric proofs like the Sine Rule and Cos (A-B) = CosACosB.. and all the rest of that bs? Completely forgot about these..

millypop

MegGustaa wrote: »

Yep, sample size n = 10, and you use the standard deviation of the means (found by dividing the SD by root n).

The expected mean of all the smaller sample is also 200, by the CLT

How do you know this is the CLT????.......cn u not jus use the empirical rule for the 95%???

Carcar123

Jones82 wrote: »

Oh ****, do we have to know the trigonometric proofs like the Sine Rule and Cos (A-B) = CosACosB.. and all the rest of that bs? Completely forgot about these..

Yeah there's eight we have to know

eefah

Tesco TripleChicken wrote: »

takes 5 mins to learn both just look it up and practice with a few problems

I have them right in front of me, but I know my own brain, and the amount of time it would take me to memorise the pattern of buttons could be much better applied cementing essay vocab for irish

Aspiring

Didn't know you could do standard deviation on your calculator till now... It's pretty much the same as finding correlation coefficient except easier.

Jones82

Carcar123 wrote: »

Yeah there's eight we have to know

Cheers, any idea which one might come up?

siobhaanx

Am I the only one that thinks paper 2 is much worse than paper 1? I've been sitting here all day trying to do paper 2 questions and I haven't been able to do any of them..