ATAR Notes: Forum
VCE Stuff => VCE Mathematics => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Mathematical Methods CAS => Topic started by: Timtasticle on November 10, 2007, 08:13:51 pm
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...is?
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Yep!
binompdf(n,p,x) = Pr(X = x)
binomcdf(n,p,x) = Pr(X ≤ x)
The "c" stands for cumulative, and that's why it's Pr(X ≤ x). If you want to find Pr(X ≤ 4), you'd accumulate the probabilities of getting X = 0, 1, 2, 3, 4.
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...is?
i believe binompdf is for one value (i.e. Pr(X=x)) whereas binomcdf is cumulative (i.e. Pr(X>x))
not 100% sure though
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Aaaah I love you FSN.
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damnit beaten.
was i even right? :?
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damnit beaten.
was i even right? :?
First one's right, second one's wrong.
binomcdf(n,p,x) = Pr(X ≤ x)
You had the arrow the other way. But cool that you've looked into it.
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Binomcdf is usually used with the terms 'at least' (1-binomcdf...)
Binompdf is usually used for exact. For instance 3 out of 5.
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does everyone have 'prcheat' the calc program??? its a time saver, especially for multi choice qns
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I only have Factor 9 .. cbf putting 10 on. Lol.
Is Prcheat necessary?..
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pr cheat is very easy to use
u have options binomial, normal, std normal etc...
and then u input mean, s.d, no of elements etc...
and then u can choose >,=,>=,<= and so forth...
no need to manually do anything
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I only have Factor 9 .. cbf putting 10 on. Lol.
Is Prcheat necessary?..
ive never actualy used it on a Q, better to do it manualy so you practise for the MC where the answers arent decimals and for the Qs where you have to show your working
when i first got it i thought "awsome" but have never even used it...
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I actually don't mind factor 9.
It is a time saver. I do not have Pr cheat though.
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does everyone have 'prcheat' the calc program??? its a time saver, especially for multi choice qns
IMO, PrCheat is a waste of time. If you know how to use your calculator, it is faster, plus you can do some questions that are not possible on PrCheat (e.g: the ones where you "n" is unknown in binomial).
PrCheat does not give you easy access the value that it returns from your calculations, so you are not sure if your accuracy too. I like using binompdf/binomcdf/invNorm/etc. because I can press Ans to use it with some further calculation down the track.
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Really only two programs are useful, I find. PrCheat and Factor9.
I'm sure most people have Factor 9.
PrCheat, does (as its name suggests) probabilities.
I actually use the inbuilt functions. I find it faster and I can use them as official working out for probability questions.
You can't write "PrCheat" as working.
Otherwise, as an alternative to the inbuilt, it's extremely handy. Just remember to break the program by pressing "ON" - quitting normally has crashed my calc and resetted my RAM (deleting itself in the process) a couple of times...
EDIT: Ah, coblin, is there anything mathematics related you DON'T know? :P
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Phew, I was wondering what Pr cheat was.
Yet different people may feel comfortable doing different things.
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So in short you don't need it.
The inbuilt means you think more and can express it as working out.
But of course, VCAA don't care as long as you can show the right answer and can prove you didn't use PrCheat to get it. (aka work out)
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I find Graphics Calc is best for Multiple Choice.
As long as you can get the right answers.
How long does anyone recommend spending on the 22 Multi Choice On Monday?
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half an hour?
i usually spend that long. 80 marks, can't spend more than 1 minute and a bit per question.
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Yeh same here. The only problem with MC is when you rush them, you tend to get more wrong(bcz some of them are tricky/dodgy/pain in the ass)
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I'm starting with the extended questions, so I don't rush them in the end.
Heh. I'm sorta nervous.
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I'm considering doing extended first. It's time-maximisation again...
Spend time on reading time doing the hard analysis questions. That's my idea. At least I have a 20% chance of guessing the MC.
I have no chance of guessing the analysis questions.
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Really only two programs are useful, I find. PrCheat and Factor9.
I'm sure most people have Factor 9.
PrCheat, does (as its name suggests) probabilities.
I actually use the inbuilt functions. I find it faster and I can use them as official working out for probability questions.
You can't write "PrCheat" as working.
Otherwise, as an alternative to the inbuilt, it's extremely handy. Just remember to break the program by pressing "ON" - quitting normally has crashed my calc and resetted my RAM (deleting itself in the process) a couple of times...
EDIT: Ah, coblin, is there anything mathematics related you DON'T know? :P
Yeah, I know maths(Ahmad) > maths(coblin) but I don't know what maths(Ahmad) - maths(coblin) equals (I know it's greater than zero!)
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Of course you don't know.
It's UNDEFINED!!! :D:D:D:D
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I think the limit approaches positive infinity.
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More like IS positive infinity. Or better still, natural log square root negative infinity with domain negative infinity.
Argh, my head hurts.
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My plan is to spot a probability question and do it first( i love prob).(15mins)
Then do some of the extended answers(slowly)(60-80 mins)
Then move on to MC (20 mins)
Check(5-20 mins)
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is it alright to write something like:
1 - binomcdf(10,0.3,2) = answer
as working for a question?
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It depends how many marks its worth. if its worth two marks then I would put some sort of extra lines, whereas if inly 1 mark i would just chuck in an answer.
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is it alright to write something like:
1 - binomcdf(10,0.3,2) = answer
as working for a question?
I would write:
Pr(X > 2) = 1 - binomcdf(10,0.3,2) = answer
Including the calculator function is acceptable, methinks. If you want to be more formal about it, I'm not sure, but they don't really care anyway.
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I think they give marks for writing what you wrote on your calculator. That's how I remember it.
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oh so we can write it like that..
i was planning to just do the binomial stuff with teh nCx(p)^x(q)^n-x
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oh so we can write it like that..
i was planning to just do the binomial stuff with teh nCx(p)^x(q)^n-x
That'd be screwed if you were doing Pr(X < 50) for n = 100.
That's where you use binomcdf :)
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oh so we can write it like that..
i was planning to just do the binomial stuff with teh nCx(p)^x(q)^n-x
That'd be screwed if you were doing Pr(X < 50) for n = 100.
That's where you use binomcdf :)
The probability they will ask that kind of question is 0.
Aside from that, I use binom commands. You can use them as working, it's listed in an Assessment report as legitimate working (and it's faster than typing out the nCr etc...)
Again, writing PrCheat is no good. Assessors are aware of PrCheat, and can't do anything about it - so they make you show working out.
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You would pretty much spend ages writing it all out.
Binomcdf becomes a good friend there.
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how would u find Pr(X => x) ?
Since binomcdf give P(X <= x) dun u have to find Pr(X=x) then minus off from the binomcdf and then take 1 - that ans?
Isn't that a bit troublesome?
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Pr(X => x) = 1 - Pr(X <= (x-1))