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# AQA A2 Mathematics MS2B Statistics 2B - 21st June 2016

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Why bother with a post grad? Are they even worth it? Have your say! 26-10-2016
1. (Original post by Suits101)
Hi I'll try an unofficial markscheme:

1
(a) 0.70291
(b) 0.6691
(c) 0.13271
(d) 0.1441
(e) 0.622

Mean = 31.7 s2 = ?

3
(a) P(X > 3) = 0.3503
(b) P (X < 3) and P (X > 3) = 0.3153
(c) Show E(X) = 3.08, Var(x) = 2.77363
(d) Poisson distribution cannot have an upper limit, people don't borrow books at a constant average rate
(e)(i) Mean = 30.8p
(e)(ii) Standard deviation = 16.7p

4
(a) k = 10
(b) P = 0.70
(c) E(X) = 0.05
(d) Integrate, ans = 1/300
(e) SD(X) = 0.02895

5
(a) Test statistic = 2.3386, CV = 2.706 so accept null
(b) comment

6
(a) Test statistic = -2.20794, reject null
(b)(i) 16.7 +- 1.80
(b)(ii) Claim not valid because 18.2 lies in CI
(c) -

7
(a) Draw graph - DENSITY function, so have to differentiate
(b) 73/24
Pretty much all of your answers are the same as mine, I'll put up a mark scheme on the first page
2. (Original post by Suits101)
Hi I'll try an unofficial markscheme:

1
(a) 0.70291
(b) 0.6691
(c) 0.13271
(d) 0.1441
(e) 0.622

Mean = 31.7 s2 = ?

3
(a) P(X > 3) = 0.3503
(b) P (X < 3) and P (X > 3) = 0.3153
(c) Show E(X) = 3.08, Var(x) = 2.77363
(d) Poisson distribution cannot have an upper limit, people don't borrow books at a constant average rate
(e)(i) Mean = 30.8p
(e)(ii) Standard deviation = 16.7p

4
(a) k = 10
(b) P = 0.70
(c) E(X) = 0.05
(d) Integrate, ans = 1/300
(e) SD(X) = 0.02895

5
(a) Test statistic = 2.3386, CV = 2.706 so accept null
(b) comment

6
(a) Test statistic = -2.20794, reject null
(b)(i) 16.7 +- 1.80
(b)(ii) Claim not valid because 18.2 lies in CI
(c) -

7
(a) Draw graph - DENSITY function, so have to differentiate
(b) 73/24
s^2 = 2.96
3. (Original post by MahuduElec)
Nice format, However you sill left it as claim may be vaild
Check edit again! Lol! We're too slow/fast for each other
4. (Original post by Suits101)
Check edit! Lol! We're too slow/fast for each other
lmao ifkr
5. (Original post by sam_97)
Pretty much all of your answers are the same as mine, I'll put up a mark scheme on the first page
Great job, thanks

Now to tally up the damage...
6. Do you think I'll get any marks for this?

I said x bar was 31.7

Then said miu was 31.7 +- whatever I worked the other part out to be (with an incorrect s^2) - I forgot about this question and rushed it at the end and hence made a mess of it
7. (Original post by Suits101)
Great job, thanks

Now to tally up the damage...
No problem, it's on the first page now!

Have you got any other maths exams left?
8. (Original post by Suits101)
Do you think I'll get any marks for this?

I said x bar was 31.7

Then said miu was 31.7 +- whatever I worked the other part out to be (with an incorrect s^2) - I forgot about this question and rushed it at the end and hence made a mess of it
Definitely. It was only 4 marks anyway, so I wouldn't worry about it too much!
9. (Original post by sam_97)
No problem, it's on the first page now!

Have you got any other maths exams left?
Finished with maths now 😄 Glad I didn't carry on with further or I'd finish way later!

10. (Original post by Suits101)
Finished with maths now 😄 Glad I didn't carry on with further or I'd finish way later!

Nice one! Which other subjects are you doing?

I've still got FP2, D1 and M2 left
11. (Original post by Suits101)
Hi I'll try an unofficial markscheme:

1
(a) 0.70291
(b) 0.6691
(c) 0.13271
(d) 0.1441
(e) 0.622

2. Mean = 31.7 s2 = 2.96

3
(a) P(X > 3) = 0.3503
(b) P (X < 3) and P (X > 3) = 0.3153
(c) Show E(X) = 3.08, Var(x) = 2.77363
(d) Poisson distribution cannot have an upper limit, people don't borrow books at a constant average rate
(e)(i) Mean = 30.8p
(e)(ii) Standard deviation = 16.7p

4
(a) k = 10
(b) P = 0.70
(c) E(X) = 0.05
(d) Integrate, ans = 1/300
(e) SD(X) = 0.02895

5
(a) Test statistic = 2.3386, CV = 2.706 so accept null
(b) comment

6
(a) Test statistic = -2.20794, reject null
(b)(i) 16.7 +- 1.80
(b)(ii) Claim not valid because 18.2 lies in CI
(c) -

7
(a) Draw graph - DENSITY function, so have to differentiate
(b) 73/24
Got pretty much the same👌
12. How did you do the one where it had the probabillity of one being less than three and the other being more than three?, 3b i think, would it not be , ( the probabillity of the first being less x the probabillity times the second being more X2! ) as they where the same probabillitys
13. how many marks would I lose for using normal instead of students t in 6b
14. (Original post by Sam1231)
How did you do the one where it had the probabillity of one being less than three and the other being more than three?, 3b i think, would it not be , ( the probabillity of the first being less x the probabillity times the second being more X2! ) as they where the same probabillitys
It looks like he did 2(0.35x0.45) to get that answer, guess I got it wrong. Brain fart and only put (0.35x0.45) = 0.1575
15. (Original post by Ayeros)
It looks like he did 2(0.35x0.45) to get that answer, guess I got it wrong. Brain fart and only put (0.35x0.45) = 0.1575
Ohh i did 0.35(1-0.35) x2 😭
16. (Original post by Sam1231)
Ohh i did 0.35(1-0.35) x2 😭
I'm not sure if we even get working out marks for these questions, I'm doubtful... I hope I haven't made other stupid mistakes too!
17. Would you get any marks for drawing F(x) even if you found f(x) in part b?
18. (Original post by Sam1231)
31.7 for the mean and 2.96 for the variance ( it asked for variance not sd by the way )
Ah, Yeah I got that. Also went for the midpoint for the mean, But I thought that was the sample mean while it wanted the population mean so I was confused, Think it's right though.

As always I couldn't think of reasons why It's not a poisson distribution, I pretty much take off two marks on every paper knowing I'll get that one wrong. What was the answer?
19. was it just 0.35x0.45 for that one question?
20. (Original post by irMike)
Ah, Yeah I got that. Also went for the midpoint for the mean, But I thought that was the sample mean while it wanted the population mean so I was confused, Think it's right though.

As always I couldn't think of reasons why It's not a poisson distribution, I pretty much take off two marks on every paper knowing I'll get that one wrong. What was the answer?
I think its because it must be open ended , and there is likelly to be peak times

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