Edexcel S2 Exam Paper January 2011 14/01/11

really silly question here - but I'm just checking... the exam is on the afternoon tomorrow not the morning... right??

Reply 162

jit987

13

Original post by airey_head

really silly question here - but I'm just checking... the exam is on the afternoon tomorrow not the morning... right??

Afternoon : 13:30pm :smile:

Reply 163

Ultimate1

Original post by LukethePianoMan

I just thought what would be mean, asking to find critical regions after a normal approximation!

How would you do that? And are there any examples? Haven't seen this yet :s-smilie:

Reply 164

jit987

13

Original post by Ultimate1

How would you do that? And are there any examples? Haven't seen this yet :s-smilie:

I'm sure I haven't also seen any questions on those :s-smilie:

Reply 165

Original post by jit987

Afternoon : 13:30pm :smile:

Haha Thankyouuu! Better to be safe than sorry :P

Good luck! :smile:

Reply 166

Original post by jit987

I'm sure I haven't also seen any questions on those :s-smilie:

Yeah there have been a couple of questions like that on some of the earlier papers...
Just really really hope nothing like that comes up :/

Reply 167

OP

Original post by LukethePianoMan

Nice to talk again :smile:

Pre exam thoughts? I am finding it pretty good so far, just hope nothing unusual comes up, like normal approximated critical regions or something!

Hello!

I'm finding it good, which feels like a shock to me! But what I am worried for is definitions >< Going to try and make sure that I am confident with them for tomorrow. Good luck!

Reply 168

dgb93

Original post by Ultimate1

How would you do that? And are there any examples? Haven't seen this yet :s-smilie:

I think you would look in the tables to find the z values of the appropriate significance level then code them back by multiplying by the standard deviation and adding the mean, then for the lower bound use the nearest integer larger than and for the upper bound use the nearest integer lower than, but this won't come up theres none in the book i dont think :s

Reply 169

warkan

3

I got two questions !! someone help me out before 5 hours !! :smile:

1.) A van company has 5 vans which they rent out by the day. Assuming that the number of vans hired out per day follows a Poisson distribution with mean 3, calculate, for a period of 100 days, the expected number of days when
-no vans will be hired
-the demand for the van is not satisfied

2.) The probability that a man is over 1.8m tall is 0.2 . A random sample of 50 men is taken and each man is measured and his height is recorded . Find the probability that the number of men in the sample over 1.8m tall is between 7 and 10 inclusive using :
-a Poisson approximation
-a normal approximation
I have found the answers to be as 0.4529(Poisson) and 0.4639(normal) and they are correct.
The next part of the question says 'By finding the actual value of the probability state which is the better approximation' . How do u go on solving this problem ? Help would be much appreciated !

Reply 170

OP

Original post by Ultimate1

How would you do that? And are there any examples? Haven't seen this yet :s-smilie:

Well if you think about it, you can do a hypothesis test on a normal distribution, like the last question on the S1 paper. I think you would make the null hypothesis based around big X (if that makes sense)

But chances of this happening, if it did it would fall into the critical region with a 1% sig level :tongue:

S1 June 2010.pdf284.4KB

Reply 171

Ultimate1

Original post by cpdavis

Well if you think about it, you can do a hypothesis test on a normal distribution, like the last question on the S1 paper. I think you would make the null hypothesis based around big X (if that makes sense)

But chances of this happening, if it did it would fall into the critical region with a 1% sig level :tongue:

Thanks I kind of get it now. I don't think it will come up though as it is not in the new book of S2. :s-smilie:

Reply 172

OP

Original post by warkan

I got two questions !! someone help me out before 5 hours !! :smile:

1.) A van company has 5 vans which they rent out by the day. Assuming that the number of vans hired out per day follows a Poisson distribution with mean 3, calculate, for a period of 100 days, the expected number of days when
-no vans will be hired
-the demand for the van is not satisfied

2.) The probability that a man is over 1.8m tall is 0.2 . A random sample of 50 men is taken and each man is measured and his height is recorded . Find the probability that the number of men in the sample over 1.8m tall is between 7 and 10 inclusive using :
-a Poisson approximation
-a normal approximation
I have found the answers to be as 0.4529(Poisson) and 0.4639(normal) and they are correct.
The next part of the question says 'By finding the actual value of the probability state which is the better approximation' . How do u go on solving this problem ? Help would be much appreciated !

For part a, you would adjust the parameter by timings your mean by 100. To work out the number of days where you expect to have no vans hired, you do P(X=0) to get your probability and times it by the number of days. Not sure what the next part means

For the poisson and normal question, you would say that a normal approximation is better in this case. This is because p is not small and close to 0.5

Reply 173

Original post by warkan

I got two questions !! someone help me out before 5 hours !! :smile:

1.) A van company has 5 vans which they rent out by the day. Assuming that the number of vans hired out per day follows a Poisson distribution with mean 3, calculate, for a period of 100 days, the expected number of days when
-no vans will be hired
-the demand for the van is not satisfied

Got an answer for your first question... I'll do the other question once I've finished typing this!

X~ Po (3)
-For 1 day => P(X=0) = e^-3 = 0.4978...
For 100 days => Ans x 100 = 4.97...days => 5 days

-For 1 day => P(X > 5) = 1 - P(X<=5) = 1 - 0.9161 = 0.0839
For 100 days => Ans x 100 = 8.39 => 9 days

I hope this is actually right!!!

Reply 174

Original post by warkan

2.) The probability that a man is over 1.8m tall is 0.2 . A random sample of 50 men is taken and each man is measured and his height is recorded . Find the probability that the number of men in the sample over 1.8m tall is between 7 and 10 inclusive using :
-a Poisson approximation
-a normal approximation
I have found the answers to be as 0.4529(Poisson) and 0.4639(normal) and they are correct.
The next part of the question says 'By finding the actual value of the probability state which is the better approximation' . How do u go on solving this problem ? Help would be much appreciated !

I got the same answers as you for the first part of this question!

The better approximation is probably Normal as n is large and p is close to 0.5 i.e. for it to be Poisson, the value of p would have to be very small

But check mark schemes to see what the 'proper' answer is :smile:

And GOOD LUCK!!

Reply 175

Firaila

9

Just did June 10 paper, found it relatively harder than the others. Would anyone else agree with this?

Reply 176

warkan

3

Original post by airey_head

Got an answer for your first question... I'll do the other question once I've finished typing this!

X~ Po (3)
-For 1 day => P(X=0) = e^-3 = 0.4978...
For 100 days => Ans x 100 = 4.97...days => 5 days

-For 1 day => P(X > 5) = 1 - P(X<=5) = 1 - 0.9161 = 0.0839
For 100 days => Ans x 100 = 8.39 => 9 days

I hope this is actually right!!!

Dude thanks so much !!! and btw the answers are correct!!! : )

Reply 177

OP