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The Edexcel S2 (24/05/12 - AM) Revision Thread

Reply 120

kanojyoxx

12

Original post by ezioaudi77

I hope they don't :redface:

Btw, how would you attempt part b?

"In a game, players select sticks at random from a box containing a large number of sticks
of different lengths. The length, in cm, of a randomly chosen stick has a continuous
uniform distribution over the interval [7, 10].

A stick is selected at random from the box.

(a) Find the probability that the stick is shorter than 9.5 cm.

To win a bag of sweets, a player must select 3 sticks and wins if the length of the longest
stick is more than 9.5 cm.

(b) Find the probability of winning a bag of sweets."

I've already answered your question??? :s-smilie:

Reply 121

john_bishop1

6

Do we have to know the proof for the variance formula of a continuous uniform distribution? As in how to get to ((b-a)^2)/12

Reply 122

whatever_x

Original post by john_bishop1

Do we have to know the proof for the variance formula of a continuous uniform distribution? As in how to get to ((b-a)^2)/12

Don't think so, it's not in the book

Reply 123

ezioaudi77

Original post by drewb

I've already answered your question??? :s-smilie:

No offence, but your method sounds complicated and this question is just for 2 marks. I was wondering whether there was an easier way.

And there is, I just found an easier way :biggrin:

But thanks anyway dude.

Reply 124

WaNaBe

1

Original post by john_bishop1

Do we have to know the proof for the variance formula of a continuous uniform distribution? As in how to get to ((b-a)^2)/12

I did a proof on the variance on a Solomon paper earlier, and a proof of E(Y^2) using integration. This was on a Solomon paper though, so doubt it would come up on a normal paper.
It's good to know anyway though, and you can figure it out as you do it, so you don't need to memorise it or anything. :smile:

Reply 125

heidi04

Yeah, just know it in case, cause it is in the book, but I highly doubt they'll ask it!
Can you guys help me with June 2011 question 7 G) and H) ? I don't get 7 H) at all, and I've seen that type of question come up a couple of times now :s-smilie:

Reply 126

Jukeboxing

8

Do we need to know that

P(|X-16| < 3)

is the same as

P(13 < X < 19)

For continous uniform distribution?

Reply 127

WaNaBe

1

Original post by Jukeboxing

Do we need to know that

P(|X-16| < 3)

is the same as

P(13 < X < 19)

For continous uniform distribution?

Again, only seen this on a Solomon paper, guess it's good to know anyway incase they decide to throw it in! :tongue:

Reply 128

Jukeboxing

8

Original post by WaNaBe

Again, only seen this on a Solomon paper, guess it's good to know anyway incase they decide to throw it in! :tongue:

Do you think the solomon papers aren't as difficult as you'd expect?

Reply 129

number23

OP

15

Original post by WaNaBe

Again, only seen this on a Solomon paper, guess it's good to know anyway incase they decide to throw it in! :tongue:

so why does the modulus thing mean you need to do a double inequality?

Reply 130

-Illmatic-

11

Original post by number23

so why does the modulus thing mean you need to do a double inequality?

If you had P([X-4]<3)

then it'd be the same as saying P(-3<X-4<3)

adding 4 on both sides to get rid of the "X-4":

P(1<X<7)

Reply 131

godknows

does anyone have any good revision notes for s2 ? please..

Reply 132

WaNaBe

1

Original post by Jukeboxing

Do you think the solomon papers aren't as difficult as you'd expect?

No they're not as difficult as I expected, I've done A, B, and C ad have scored well on them so far. Having said that, I have scored on average about 3 marks more on the normal papers.

How have you found them?

Reply 133

Jukeboxing

8

Original post by WaNaBe

No they're not as difficult as I expected, I've done A, B, and C ad have scored well on them so far. Having said that, I have scored on average about 3 marks more on the normal papers.

How have you found them?

I've been able to do majority of the questions with the exceptions of unfamiliar questions like the one I mentioned above.

Done them all, so i'm going to do some edexcel papers now.

Reply 134

goku12

hi, are you guys going to learn how to derive the Var(x) formula??

Reply 135

Braniac101

2 questions guys

1. if signifance level is 0.05, and p(X<=x) is equal to 0.05, then do you reject null hypothesis if you are testing at 5% level?
2. when you find F(x) from f(x) or vice versa, do you have to factorise the equation formed. in the markcheme, they usually so, just wandering wether you have to
thanks

Reply 136

Mathematix

2

Original post by Jukeboxing

Do we need to know that

P(|X-16| < 3)

is the same as

P(13 < X < 19)

For continous uniform distribution?

Probably not, but it's easy enough to work out anyway.

How's everyone finding the papers? :biggrin:

Reply 137

knowledgecorruptz

9

Original post by Braniac101

2 questions guys

1. if signifance level is 0.05, and p(X<=x) is equal to 0.05, then do you reject null hypothesis if you are testing at 5% level?
2. when you find F(x) from f(x) or vice versa, do you have to factorise the equation formed. in the markcheme, they usually so, just wandering wether you have to
thanks

1. I think so. I mean, the chances of this happening are ridiculously low but normally in two-tailed tests they ask for a critical region "close to 2.5%", and sometimes the actual significance level is above it so that's my guess.

2. Definitely not.

Reply 138

exam2k10

9

Is it possible to get 90+ UMS in this module, because I am scoring about 62ish/75?

Reply 139

master_blaster66

17

Original post by exam2k10

Is it possible to get 90+ UMS in this module, because I am scoring about 62ish/75?

well obviously its possible to get 90+UMS...but with 62/75, it will be hard even getting 80UMS, as the boundaries have been high recently, except june11 i think

The Edexcel S2 (24/05/12 - AM) Revision Thread

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