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

1. (Original post by sam_97)
How did everyone find the exam overall? Similar difficulty to last year?
I think it was a fair bit easier than last year's - I think A* will be around 68-69
2. (Original post by sam_97)
I got 0.622 as well
(Original post by tanyapotter)
I got 0.622 :/
I did (1-P(X<=0)(1-P(X<=0)(1-P(X<=0) for all 3 and multiplied it, was that the right method?

I may have just inputted a value incorrectly
3. (Original post by sam_97)
I think that is the value I got, although I rounded it to 2.34
Yup

What did you put for the comment?
4. This is the kind of exam where the answers are random decimals and I really really really can't remember any of it. I remember some if people say it but everything's a Blurr after I walk out.

I feel like I've lost a couple on "comment" questions but it was an okay paper I think. I preferred it to last years. Any predictions for A* boundaries?
5. (Original post by Suits101)
I did (1-P(X<=0)(1-P(X<=0)(1-P(X<=0) for all 3 and multiplied it, was that the right method?

I may have just inputted a value incorrectly
That is the method I used as well. Even if your final answer is incorrect, you will have picked up method marks for definite.
6. (Original post by Suits101)
I did (1-P(X<=0)(1-P(X<=0)(1-P(X<=0) for all 3 and multiplied it, was that the right method?

I may have just inputted a value incorrectly
P(X<=0) is the same as P(X=0) - maybe that's where you went wrong?
7. Hey guys! I had time at the end of the exam so I wrote down most (not all) of the answers I put on my calculator. Obviously some will likely be wrong but here's what I put so we can compare:
1) 0.703, 0.870, 0.133, 0.144, 0.622
2) mean=31.7 sd^2=2024.4
3) 0.35, 0.315, 2.77, 31p, £2.77
4) 0.7, sd(x)=0.0289
5) Z=2.34
6) (can't remember what I put for crit value of island A lizards), Mu(B)=15.1cm
7) For graph I had straight horizontal line from (1, 1/4) to (4, 1/4) and then straight line going down to (6,0) and 0 otherwise.
E(X)=3.04
Let me know if you think any are wrong (i think 1b might be). Thanks!
8. (Original post by tanyapotter)
P(X<=0) is the same as P(X=0) - maybe that's where you went wrong?
It's the same thing - damn must've inputted it wrong!

(Original post by sam_97)
That is the method I used as well. Even if your final answer is incorrect, you will have picked up method marks for definite.
Thanks

I'm just glad that I should be able to get one mark on that question as I had no idea!
9. (Original post by Suits101)
Yup

What did you put for the comment?
I failed to reject Ho, as 2.34 lies outside the critical region. Then I made some comment in context about there being no association between the type of engine and car problems.
10. (Original post by Suits101)
I did that but accepted H0.

You can't accept or reject H1, only accept or reject H0.
Yeah that's what I wrote so it's all good
11. (Original post by df97)
Hey guys! I had time at the end of the exam so I wrote down most (not all) of the answers I put on my calculator. Obviously some will likely be wrong but here's what I put so we can compare:
1) 0.703, 0.870, 0.133, 0.144, 0.622
2) mean=31.7 sd^2=2024.4
3) 0.35, 0.315, 2.77, 31p, £2.77
4) 0.7, sd(x)=0.0289
5) Z=2.34
6) (can't remember what I put for crit value of island A lizards), Mu(B)=15.1cm
7) For graph I had straight horizontal line from (1, 1/4) to (4, 1/4) and then straight line going down to (6,0) and 0 otherwise.
E(X)=3.04
Let me know if you think any are wrong (i think 1b might be). Thanks!
Hi!

I agree with all but 1(b) I got 0.669
12. (Original post by Suits101)
This is what I remember and it MAY NOT BE RIGHT

1(a) 0,7029
1(b) 0.669
1(c) 0.1327
1(d) 0.144
1(e) 0.462 (should be 0.622?)

2. Mean = ? s2 = ?

3(a) 0.350
3(b) 0.1575
3(c) Var(x) = 2.7736
3(d) Poisson cannot have an upper limit, people don't borrow books at a constant average rate
3(e)(i) 30.8p
3(e)(ii) 5.27p

4
(a) k = 10
(b) P = 0.70
(c) E(X) = 0.05
(d) Integrate, ans = 1/300
(e) SD(X) = 0.0289

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

7(a) Draw graph - DENSITY function, so have to differentiate
7(b) 61/6 but I got it wrong
1e was 0.622

3b, you had to do 0.35x0.45x2, as there were 2 combinations
3d. 1st I agree, 2nd point I said P(X=x)=0, which implies e^(-lambda)=0 which is nonsense
2eii. asked fro variance, not sd
13. (Original post by Krithika256)
65-A 70-A*, more or less the same as 2014 and 1025, maybe closer to the lower of the two
14. (Original post by MahuduElec)
1e was 0.622

3b, you had to do 0.35x0.45x2, as there were 2 combinations
3d. 1st I agree, 2nd point I said P(X=x)=0, which implies e^(-lambda)=0 which is nonsense
2eii. asked fro variance, not sd
I was going to do that for 3(b) - damn!

3(e)(ii) - are you sure? Damn!
15. (Original post by Salty carpet)
Same. Anyone remember their chi^2 value or how they found it? I merged the first two columns and then used Yate's correction... can't remember my value, although I did reject H1
2.3ish and accepted H0, so reject H1 yes (although you should put acceot H0)
16. 0.703
0.669
0.133
0.144
0.622

mean - 31.7 o^2 - can't remember

0.35
0.158
2.77
30.8
16.7
10
0.7
0.05
1/300
root3 / 60
14.9
18.5

ANSWER DUMP. didn't do the last 4 marker.
17. I think I said there was association between the engine and mechanical problems, meaning it would be tough to still get the 2 marks for the comment after. I think I mentioned that one of the expected values for Diesel was considerably lower than the actual value and tried to use this to suggest why there was association. I used all the correct terms and stuff, do you think I would still get 2 marks for the comment?
18. (Original post by sam_97)
How did everyone find the exam overall? Similar difficulty to last year?
About the same yes, the last Q in both had sneaky tricks
19. (Original post by tanyapotter)
I think it was a fair bit easier than last year's - I think A* will be around 68-69
Agreed. I don't think the grade boundaries will change much compared to last year to be honest, 70+ will definitely be an A*.

(Original post by KB_97)
This is the kind of exam where the answers are random decimals and I really really really can't remember any of it. I remember some if people say it but everything's a Blurr after I walk out.

I feel like I've lost a couple on "comment" questions but it was an okay paper I think. I preferred it to last years. Any predictions for A* boundaries?
Sometimes they can be really picky with the explain questions so it's easy to drop a couple of marks here and there, even if you think your answer is correct.

I think the boundary for A* will be somewhere between 67-69, but it is always difficult to tell. Best to wait until the day before results day to find out
20. (Original post by Suits101)
Hi!

I agree with all but 1(b) I got 0.669 and 3(b) I got 0.1575 (0.35 x 0.45 - may be wrong) and 3(e)(ii) I got 5.27p (may be wrong)
For 3(b) I did 2(0.35 x 0.45) as there are two possible ways of people taking out the books (either first guy got out more than 3 and second got out less than 3 or vice versa). Not sure if I'm right but either way we have very similar answers which is good news!
For 3(e)(ii) I did 2.77 x 10^2 as var(aX)=a^2var(X), likewise I'm unsure on this one too.

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