The Official Edexcel S2 Jan 2010 Thread

So, how did everyone find it?
What do you think grade boundaries will be like?

Reply 23

amzmalhotra

I found it quite easy apart from the last subquestion which I didnt revise. Just waiting for answers to be posted!

Reply 24

JNV

amzmalhotra

I found it quite easy apart from the last subquestion which I didnt revise. Just waiting for answers to be posted!

I luckily revised that this morning

Reply 25

What was the last subquestion?

Reply 26

Anyone has answers to the test? Did any of you ask the teacher for them? I will rep for answers :smile:

Reply 27

Clarity Incognito

11

From the ones I can remember:

The one that turns out to be a continuous uniform distribution, part (e) P(X=1) = 0

Last question. You find the mean the usual way and the variance for that matter, list out all possible samples, there are 8.

Probability of mean value
1 is 1/64,
4/3 is 9/64
5/3 is 27/64
2 is 27/64

You had to use Po(1/4) and Po(2/5) For the robot.

Probability that it breaks down in the subsequent 8 hours is 2/5, mutually exclusive.

Really cannot remember much more, if anyone can jog my memory, I can try and verify.

Reply 28

Here are my answers:

question 1.
a) A~B(20,0.05)
b) 0.3585
c) 0.0026
d) mean=1 Var(x)=0.95

question 2.
a) 1/12
b) f(x)=1/6 for -2<=x<=4
f(x)=0 otherwise

c) Uniform rectangular
d) Var(x)=3
e) 0

question 3.
a) 0.7788
b) 0.3297
c) 0.0536
d) 0.03297 (independence)

question 4.
a) k=1/9
b) F(x)=0 for x<=0
F(x)=1/9( x^3/3 -x^2 +2x) for 0<x<=3
F(x)=x/3 -1 for 3<x<=4
F(x)=1 for x>=4

c) mean=2.4167
d) I only used the equation for 0-3 range, change of sign indicates root in between

question 5.
a) 0.3328
b) 0.0485

question 6.
a) x<=2 x>=16
c) 0.85%

question 7.
a) mean=1.75 Var(x)=0.1875
b) list of all samples
c) increasing mean, prob: 1/64, 9/64, 27/64, 27/64

DISCLAIMER: THEY ARE NOT 100% RIGHT ANSWERS, THEY ARE JUST MY ANSWERS FROM THE TEST, THERE ARE MISTAKES HERE.

Reply 29

Oh yh, last question was on sampling dist.

Reply 30

BrightGirl

15

Clarity Incognito

You had to use Po(1/4) and Po(2/5) For the robot.

Probability that it breaks down in the subsequent 8 hours is 2/5, mutually exclusive.

Damn got that wrong then, I put that it would be the answer you worked out for p(x>=1) because breakdowns are indpendant/happen at a constant rate.

Reply 31

Moa

Here are my answers:

question 1.
a) A~B(20,0.05)
b) 0.3585
c) 0.0026
d) mean=1 Var(x)=0.95

question 2.
a) 1/12
b) f(x)=1/6 for -2<=x<=4
f(x)=0 otherwise

c) Uniform rectangular
d) Var(x)=3
e) 0

question 3.
a) 0.7788
b) 0.3297
c) 0.0536
d) 0.03297 (independence)

question 4.
a) k=1/9
b) F(x)=0 for x<=0
F(x)=1/9( x^3/3 -x^2 +2x) for 0<x<=3
F(x)=x/3 -1 for 3<x<=4

was it not x/3 -1/3

F(x)=1 for x>=4

c) mean=2.4167
d) I only used the equation for 0-3 range, change of sign indicates root in between

question 5.
a) 0.3328
b) 0.0485

question 6.
a) x<=2 x>=16
c) 0.85%

hypoth. testing question right, 15 was not in critcial region. actual significan was like 0.7%, summin less than 1%

question 7.
a) mean=1.75 Var(x)=0.1875
b) list of all samples
c) increasing mean, prob: 1/64, 9/64, 27/64, 27/64

was it not x/3 -1/3

hypoth. testing question right, 15 was not in critcial region. actual significan was like 0.7%, summin less than 1%

Reply 32

Clarity Incognito

11

Moa

Here are my answers:

question 1.
a) A~B(20,0.05)
b) 0.3585
c) 0.0026
d) mean=1 Var(x)=0.95

question 2.
a) 1/12
b) f(x)=1/6 for -2<=x<=4
f(x)=0 otherwise

c) Uniform rectangular
d) Var(x)=3
e) 0

question 3.
a) 0.7788
b) 0.3297
c) 0.0536
d) 0.03297 (independence)

question 4.
a) k=1/9
b) F(x)=0 for x<=0
F(x)=1/9( x^3/3 -x^2 +2x) for 0<x<=3
F(x)=x/3 -1 for 3<x<=4
F(x)=1 for x>=4

c) mean=2.4167
d) I only used the equation for 0-3 range, change of sign indicates root in between

question 5.
a) 0.3328
b) 0.0485

question 6.
a) x<=2 x>=16
c) 0.85%

question 7.
a) mean=1.75 Var(x)=0.1875
b) list of all samples
c) increasing mean, prob: 1/64, 9/64, 27/64, 27/64

Good memory, I agree with all of q.1, 2 and 7. Unfortunately I can't remember enough of the rest to be sure. Anwyays, hi5.

EDIT Apart from 2a) which I've just read again, and other people have checked.

Reply 33

man u

Moa

Here are my answers:

question 1.
a) A~B(20,0.05)
b) 0.3585
c) 0.0026
d) mean=1 Var(x)=0.95

question 2.
a) 1/12
b) f(x)=1/6 for -2<=x<=4
f(x)=0 otherwise

c) Uniform rectangular
d) Var(x)=3
e) 0

question 3.
a) 0.7788
b) 0.3297
c) 0.0536
d) 0.03297 (independence)

question 4.
a) k=1/9
b) F(x)=0 for x<=0
F(x)=1/9( x^3/3 -x^2 +2x) for 0<x<=3
F(x)=x/3 -1 for 3<x<=4
F(x)=1 for x>=4

c) mean=2.4167
d) I only used the equation for 0-3 range, change of sign indicates root in between

question 5.
a) 0.3328
b) 0.0485

question 6.
a) x<=2 x>=16
c) 0.85%

question 7.
a) mean=1.75 Var(x)=0.1875
b) list of all samples
c) increasing mean, prob: 1/64, 9/64, 27/64, 27/64

I got mostly the same answers but for the cdf i got 1/3x -1/3

Reply 34

Also someone said high grade boundaries. How high approx. 68+ for an A?

Reply 35

Posting the whole paper in few seconds

Reply 36

khaggy

I thought that was a very good paper. I expect boundaries to at least 65/66

Reply 37

qstns 2(a), was mean not 1, 1/2(a+b), can see this from f(x) in later part of question

Reply 38