# S2 exam official thread Watch

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#21

I was the only one in the whole hall Got very lonely and cold. Don't want to say how I found it because it always jinxes my result...hehe

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#22

(Original post by

Yep.. Edexcel.. personally found the paper very good - am happy with it - had 30 mins left for question 7 at the end

My recollection of exam:

1)a) Given R~B(15,0.3) -- find P(R=5) ...

1)b) Given S~Po(7.5) -- find P(S=5) ...

a)c) Given T~N(8,2^2) -- find P(T=5) ...

2)a)i) What is a population

2)a)ii) What is a Sample Frame (2)

2)b) Explain why sample frame != population (1)

2)c) Give an example with reason of Census & Sample(4)

3)a)Stick of length 2l is broken into two... define pdf of length of shorter half .

3)b) P(X< l/3)...

3)c) E(X) ......

3)d) P(Both broken sticks being of length l/3)...

4)a) Give two additional conditions of binomial (2)

4)b) Perform hypothesis test with 1% significance level.. I remember I ended up doing normal distribution...

4)c) Commet on assumption... think this had to do with the interpolation ..

5)a) Defecient article has probability of 0.032 ... so find probability of exactly two articles being defficient out of 10 articles...

5)b) Sample size increased to 100 ... as n is large p is small... use poisson...

5)c) Sample size increased further to 1000... approximate to poisson first with mean 32.. then approximate to normal... eventually got answer of

6)a) Accidents on a particular stretch of road had mean of 3 per month, evaluate probability of there being more than 4 in a month...

6)b) Probability of there being more than 4 in 3 months (I think)...

6)c) Do hypothesis test with 5% significance level to see if need speed regulation measures have made an impact given only 1 accident per month nor on average...

6)d) Do hypothesis test with 5% to see if new speed regulation has had an affect given only 55 accidents in 2 years...

7)a) Show k = 2/9 (3)

7)b) Find E(X) ...

7)c) Find Mode(X) ...

7)d) Find the CDF...

7)e) P(X <= 2.5)

7)f) Deduce Median... and comment on distribution...

Absolutely loved question seven.. cos you could see where it was going.. and you knew it was right when it said "deduce the median.. and comment on the distribution"

MdSalih

**MdSalih**)Yep.. Edexcel.. personally found the paper very good - am happy with it - had 30 mins left for question 7 at the end

My recollection of exam:

1)a) Given R~B(15,0.3) -- find P(R=5) ...

**0.2061**(2)1)b) Given S~Po(7.5) -- find P(S=5) ...

**0.1094**(1)a)c) Given T~N(8,2^2) -- find P(T=5) ...

**0**(1)2)a)i) What is a population

2)a)ii) What is a Sample Frame (2)

2)b) Explain why sample frame != population (1)

2)c) Give an example with reason of Census & Sample(4)

3)a)Stick of length 2l is broken into two... define pdf of length of shorter half .

**Uniform/Rectangular Distribution...**

f(x) = 1/l for 0 < x < l // 0 otherwise(3)f(x) = 1/l for 0 < x < l // 0 otherwise

3)b) P(X< l/3)...

**1/3**(2)3)c) E(X) ......

**l/2**(1)3)d) P(Both broken sticks being of length l/3)...

**(1/9)**(2)4)a) Give two additional conditions of binomial (2)

4)b) Perform hypothesis test with 1% significance level.. I remember I ended up doing normal distribution...

**1 - phi(3.06)... interpolated as it wasn't in table got 0.011 - insignificant result.**(6)4)c) Commet on assumption... think this had to do with the interpolation ..

__think__your ment to comment on that.. not sure (2)5)a) Defecient article has probability of 0.032 ... so find probability of exactly two articles being defficient out of 10 articles...

**0.0355**(3)5)b) Sample size increased to 100 ... as n is large p is small... use poisson...

**0.6025**(4)5)c) Sample size increased further to 1000... approximate to poisson first with mean 32.. then approximate to normal... eventually got answer of

**0.0294**(6)6)a) Accidents on a particular stretch of road had mean of 3 per month, evaluate probability of there being more than 4 in a month...

**0.1847**(3)6)b) Probability of there being more than 4 in 3 months (I think)...

**0.945**(2)6)c) Do hypothesis test with 5% significance level to see if need speed regulation measures have made an impact given only 1 accident per month nor on average...

**0.1991 > 0.05 -- so not sigificant.**(4)6)d) Do hypothesis test with 5% to see if new speed regulation has had an affect given only 55 accidents in 2 years...

**0.0262 < 0.05 - significant result.**(7)7)a) Show k = 2/9 (3)

7)b) Find E(X) ...

**2.5**(3)7)c) Find Mode(X) ...

**2.5**(2)7)d) Find the CDF...

**F(X) = 0 for x < 1 // (1/27)*(-2x^3 + 15x^2 -24x + 11) for 1 <= x <= 4 // 1 for x > 4**(5)7)e) P(X <= 2.5)

**0.5**(2)7)f) Deduce Median... and comment on distribution...

**m = 2.5 as F(2.5) = 0.5 .. distribution is symmetrical.**(2)Absolutely loved question seven.. cos you could see where it was going.. and you knew it was right when it said "deduce the median.. and comment on the distribution"

*[Edit]Marking scheme (given in red) should now be correct**[Edit2]Corrections made to Question 5 - thanks to the person who pointed them out.. don't know forum nick*MdSalih

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(Original post by

I don't think your correct on question 4. For part b if you look up Ph of 3.06 its 0.9989 so 1-0.9989 is 0.0011 not 0.011. Hence result IS significant. Correct me if I'm wrong?

**dieeiervonsatan**)I don't think your correct on question 4. For part b if you look up Ph of 3.06 its 0.9989 so 1-0.9989 is 0.0011 not 0.011. Hence result IS significant. Correct me if I'm wrong?

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#24

**dieeiervonsatan**)

I don't think your correct on question 4. For part b if you look up Ph of 3.06 its 0.9989 so 1-0.9989 is 0.0011 not 0.011. Hence result IS significant. Correct me if I'm wrong?

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#25

(Original post by

yes it was 0.0011, but the significane leve was 1% wasnt it?

**Syncman**)yes it was 0.0011, but the significane leve was 1% wasnt it?

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#26

I have a question.. have a bad feeling I rounded most answers to 3sf, is that bad? Or do they only accept 4sf ?

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(Original post by

I have a question.. have a bad feeling I rounded most answers to 3sf, is that bad? Or do they only accept 4sf ?

**dieeiervonsatan**)I have a question.. have a bad feeling I rounded most answers to 3sf, is that bad? Or do they only accept 4sf ?

....& yes, 0.0011 < 0.01 so it is significant as it lies within the critical region.

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#28

(Original post by

On the old mark schemes they tended to accept 3 or 4 s.f, i just used 4 s.f...dont think it will matter too much though!

....& yes, 0.0011 < 0.01 so it is significant as it lies within the critical region.

**jmzcherry**)On the old mark schemes they tended to accept 3 or 4 s.f, i just used 4 s.f...dont think it will matter too much though!

....& yes, 0.0011 < 0.01 so it is significant as it lies within the critical region.

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#29

(Original post by

Yes, so 1% is 0.01 and since 0.0011<0.01 then the result is significant right?

**dieeiervonsatan**)Yes, so 1% is 0.01 and since 0.0011<0.01 then the result is significant right?

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#30

i didnt take into account the fact it was the shorter section of the rod in q3 (i think) so got the wrong interval - hope there are sum follow through marks!

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#31

(Original post by

Yeh you are right i think...that was the beans question werent it? 0.1 prob, 250 kids etc....40 guessed the difference. If thats the same question then it was sig and there was evidence to suggest the 10% claim was inncorrect!!

**jmzcherry**)Yeh you are right i think...that was the beans question werent it? 0.1 prob, 250 kids etc....40 guessed the difference. If thats the same question then it was sig and there was evidence to suggest the 10% claim was inncorrect!!

MdSalih

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#33

(Original post by

Just got back from my S2 exam, didnt find it too taxing so hopefully the UMS marks will come flying in! How did everyone else find it?

**jmzcherry**)Just got back from my S2 exam, didnt find it too taxing so hopefully the UMS marks will come flying in! How did everyone else find it?

I thought that there was simply too much to do for Edexcel S2. I dropped around four marks due to running out of time.

John

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#34

(Original post by

I was the only one in the whole hall Got very lonely and cold. Don't want to say how I found it because it always jinxes my result...hehe

**PhoenixSTL**)I was the only one in the whole hall Got very lonely and cold. Don't want to say how I found it because it always jinxes my result...hehe

John

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#35

(Original post by

got 95% first time round in june GO MEE!!

lol

**kevins**)got 95% first time round in june GO MEE!!

lol

This time around I made sure that I showed far more workings. I hope to get over 80%, but you never know!

JP

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#36

(Original post by

Yep.. Edexcel.. personally found the paper very good - am happy with it - had 30 mins left for question 7 at the end

My recollection of exam:

1)a) Given R~B(15,0.3) -- find P(R=5) ...

1)b) Given S~Po(7.5) -- find P(S=5) ...

a)c) Given T~N(8,2^2) -- find P(T=5) ...

2)a)i) What is a population

2)a)ii) What is a Sample Frame (2)

2)b) Explain why sample frame != population (1)

2)c) Give an example with reason of Census & Sample(4)

MdSalih

**MdSalih**)Yep.. Edexcel.. personally found the paper very good - am happy with it - had 30 mins left for question 7 at the end

My recollection of exam:

1)a) Given R~B(15,0.3) -- find P(R=5) ...

**0.2061**(2)1)b) Given S~Po(7.5) -- find P(S=5) ...

**0.1094**(1)a)c) Given T~N(8,2^2) -- find P(T=5) ...

**0**(1)2)a)i) What is a population

2)a)ii) What is a Sample Frame (2)

2)b) Explain why sample frame != population (1)

2)c) Give an example with reason of Census & Sample(4)

MdSalih

Also, I had a guess for 2 (b). I wrote that the sample frame may not be up to date so the list may not have every member of the population. Reasonable?

JP

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#37

**dieeiervonsatan**)

I have a question.. have a bad feeling I rounded most answers to 3sf, is that bad? Or do they only accept 4sf ?

I always show the full number, and then show it to 4dp.

JP

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#38

(Original post by

I thought that the Edexcel S2 paper was dead easy in June. I spanked the paper, only to find that I got only a pathetic 53%!! I have had it remarked (no change) and getting it back did not make me understand the problem.

This time around I made sure that I showed far more workings. I hope to get over 80%, but you never know!

JP

**John Porcella**)I thought that the Edexcel S2 paper was dead easy in June. I spanked the paper, only to find that I got only a pathetic 53%!! I have had it remarked (no change) and getting it back did not make me understand the problem.

This time around I made sure that I showed far more workings. I hope to get over 80%, but you never know!

JP

OCR - you screwballs

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#39

(Original post by

I did D1 last summer and i got a miserable D (50 UMS) only to have it remarked to 79 UMS

OCR - you screwballs

**manps**)I did D1 last summer and i got a miserable D (50 UMS) only to have it remarked to 79 UMS

OCR - you screwballs

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