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# Edexcel S2 Exam Paper January 2011 14/01/11 Watch

1. (Original post by bekah1234)
yeh i did exactly the same, but i got that the teacher's claim was right and that she was guessing? :/
Yeah thats what i got too.

Accept HO, The teachers claims were correct.
2. (Original post by warkan)
i second that!
3. For thee very last question what did u guys do?? i got smtin around 0.4 smtin as the probbality..
I did 1-[p(x=0)+p(x=1)] using the binomial formula and previous questions probabilty..
4. (Original post by warkan)
For thee very last question what did u guys do?? i got smtin around 0.4 smtin as the probbality..
I did 1-[p(x=0)+p(x=1)] using the binomial formula and previous questions probabilty..
I did something like this, but i had to round the answers from the previous question? Then used a binomial dist.
5. (Original post by sete)
I did something like this, but i had to round the answers from the previous question? Then used a binomial dist.
well i didn't round from previous question..i just used the fraction...
6. I got 0.478 as intermediate of something and then further did binomial of something 3 (people???) and got 0.8908

Can anyone put up at least question paper????????
7. (Original post by warkan)
well i didn't round from previous question..i just used the fraction...

(Original post by cazzy-joe)
I got 0.478 as intermediate of something and then further did binomial of something 3 (people???) and got 0.8908

Can anyone put up at least question paper????????
I got 0.478 too but then rounded the probability and used the tables to answer the next question. So I suspect i did that wrong. I did X ¬ B(5,0.5) to answer the next question. Or did i use a Poisson and X¬Po(2.5)? I can't remember exactly, MEH.

What you guys did is probably right, using the same probability and working it out using the binomial formulae.
8. (Original post by sete)
I got 0.478 too but then rounded the probability and used the tables to answer the next question. So I suspect i did that wrong. I did X ¬ B(5,0.5) to answer the next question.

What you guys did is probably right, using the same probability and working it out using the binomial formulae.
yes it is better to use the exact binomial formula seeing that n is only 3. I don't think anyone will post model answers - if i remember correctly the guy who is doing the S1 answers (Arsey) said he wasn't going to do S2.
9. I'll post what I can remember:

The two hypotheses tests: accepted teacher's claim that student guessed. Reject H0 in ferry question so the ferry service had improved.

For the E(X), Var (X), etc question I had 1, 4/3, 7/3, 0.6 (i think) then can't remember if there was any more.

There was a normal approximation somewhere which I got a pretty small answer for (<0.1 from what i remember.)

For the 4-8x=0 question I had the median as 0.146 i think and the mode as 0 so there was a positive skew.

For the last question I had the mean as 4.8, then part c was just over 3000/6561 i think.
10. As far as I remember my answers were: In any random order

M=15

Teacher question about guessing accept Ho because it was around 0.12..>0.05 so teacher claim was correct.

Question about ferry was reject Ho, because it was around 0.04..<0.05 so the ferry had improved in how late it was.

Positive skewness as Mean>Median>Mode...I calculated Mean to make sure which was 1/6..>Median(0.146...)> Mode(0)

Got some fraction like 3145/6561 for some answer. Then used that answer for the next part as Binomial (3 , 3145/6561) and did 1 - P(X=0)+P(X=1) using the formula.

Approximating the Poisson as Normal got P(Z< -2.1), then 1- P(Z< 2.1).

Finished the paper in 55 minutes but left the 5 marks uniform question out. Got confused with that question and even with 35 minutes to spare couldn't get the right method of (40, 0.25). I did another method of drawing the sketch with interval [-40 ,120]. P(X>=10) equalled the negative part of the graph and by doing this got answer of 3/4.(which sounded reasonable so left it with that) But after coming out of the exam lots of people did (40,0.25)...so lost the marks, any know if I will get 1/2 method marks?

Can't remember other answers...Someone at least post the QP or MS??????????
11. (Original post by cpm1)
I'll post what I can remember:

The two hypotheses tests: accepted teacher's claim that student guessed. Reject H0 in ferry question so the ferry service had improved.

For the E(X), Var (X), etc question I had 1, 4/3, 7/3, 0.6 (i think) then can't remember if there was any more.

There was a normal approximation somewhere which I got a pretty small answer for (<0.1 from what i remember.)

For the 4-8x=0 question I had the median as 0.146 i think and the mode as 0 so there was a positive skew.

For the last question I had the mean as 4.8, then part c was just over 3000/6561 i think.
Same

(Original post by jit987)
As far as I remember my answers were: In any random order

M=15

Teacher question about guessing accept Ho because it was around 0.12..>0.05 so teacher claim was correct.

Question about ferry was reject Ho, because it was around 0.04..<0.05 so the ferry had improved in how late it was.

Positive skewness as Mean>Median>Mode...I calculated Mean to make sure which was 1/6..>Median(0.146...)> Mode(0)

Got some fraction like 3145/6561 for some answer. Then used that answer for the next part as Binomial (3 , 3145/6561) and did 1 - P(X=0)+P(X=1) using the formula.

Approximating the Poisson as Normal got P(Z< -2.1), then 1- P(Z< 2.1).

Can't remember other answers...Someone at least post the QP or MS??????????
Same but now I think I did last question wrong I remember I did 3C0+3C1+3C2
12. (Original post by aneesh)
But should H0 be p = 0.4 and H1 be p < 0.4
As the teacher assumes that she guessed
The teacher's assumption is the null hypothesis, since you're testing his/her claim, so the alternative is that the student didn't guess, i.e. they have a higher chance than 0.2 (1/5)
13. (Original post by Geniusmiss)
the server must be down...it'll take a bit..try this link- http://www.xtremepapers.net/Edexcel/...ed/S1/Solomon/
Could you help me out again sorry! I'm having trouble finding D1 Solomon papers on the xtremepapers site?
14. Arrgh, in the normal approximation I forgot to account for the cotinuity correction. How many marks will I lose, do you think?
15. But shouldnt the assumption always the alternative hypothesis ?
Thats what my teacher told me
16. (Original post by ChopinLiszt)
Arrgh, in the normal approximation I forgot to account for the cotinuity correction. How many marks will I lose, do you think?
You'll lose one for not applying the continuity correction, then maybe another one for accuracy at the end of the question. You'll still get the method marks each sie of the continuity correction though.
17. (Original post by cazzy-joe)
Same

Same but now I think I did last question wrong I remember I did 3C0+3C1+3C2
If I remember correctly I think the question said at least two. Could have said exactly two I don't remember.
18. Forgot to set my median to 0.5 so therefore got the skewness wrong to, anyone know how many marks the median and skewness were worth?!
19. (Original post by aneesh)
But shouldnt the assumption always the alternative hypothesis ?
Thats what my teacher told me
It usually is, but the null hypothesis has to be a fixed probability, and if the student isn't guessing, it isn't fixed - they could get anything between 1 and 10 out of 10. So we have to use the probability of getting it right by guessing (0.2) as it is the only fixed one available. The 4 out of 10 is only the result of 1 trial, it can't be turned into a probability.

So
H0 : p=0.2
H1 : p>0.2 (they're more likely to get it right if they aren't guessing)

At least I think that's right.

^Sorry if it doesn't make sense, it's a weird question and hard to explain!
20. (Original post by mashman9)
Forgot to set my median to 0.5 so therefore got the skewness wrong to, anyone know how many marks the median and skewness were worth?!
Well if you reached the correct conclusion from your answers I think they have to at least give you one mark for method, maybe two if it says ft (follow through) on their mark scheme

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