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# Official Edexcel S3 thread Wednesday 20 May 2015 Morning [6691] watch

1. What was the s.d. for the first sample on Q4, which you used in (b)?
2. Somehow managed to do the hypotheses the wrong way round for the contingency table bit at the end...didn't check any answers

I think I've probably dropped over 10 marks; and none of them on the question that was actually somewhat tricky, I can hardly complain, just stupidity

This is one of the easiest modules too, nevermind an a* an a might be out of my grasp at this rate
3. (Original post by Bayestheorem)
can someone please post 6a solution????

Also how many marks for 5d arriving at 0.181 again as quite a few people did it, 0? eg for (their value......) in mark scheme?

i messed up on 6a) - I'm really hoping for someone to post it!!!
4. How many A2 modules are you doing?
5. Is no one going to make a proper unofficial mark scheme?? Like the ones arsey made?
6. right, nobody seems to be doing 6a, so here's a written attempt:

H0: U[0,10] is a suitable model for these data
H1: U[0,10] is not a suitable model for these data

E(X)'s: 40, 30, 20, 10

Test stat=13.65

v=3

cv=11.345 as 1% 3df

test stat > cv so reject H0,

U[0,10] is not a suitable model.
7. (Original post by varshanct95)
i messed up on 6a) - I'm really hoping for someone to post it!!!
I did H0: U[0, 10] is a good model
H1: It isn't

And then Expected frequencies for each colour were

40, 30, 20, 10

I had a test statistic of around 13.something
v = 3, Critical region was like 11.something
Reject H0, U[0,10] not a good model
8. What would get you 2 marks for 2b) - I got not necessary. but i didn't the get the reason?
9. 9/9
(Original post by 13 1 20 8 42)
I did H0: U[0, 10] is a good model
H1: It isn't

And then Expected frequencies for each colour were

40, 30, 20, 10

I had a test statistic of around 13.something
v = 3, Critical region was like 11.something
Reject H0, U[0,10] not a good model
10. (Original post by Bayestheorem)
right, nobody seems to be doing 6a, so here's a written attempt:

H0: U[0,10] is a suitable model for these data
H1: U[0,10] is not a suitable model for these data

E(X)'s: 40, 30, 20, 10

Test stat=13.65

v=3

cv=11.345 as 1% 3df

test stat > cv so reject H0,

U[0,10] is not a suitable model.
perfect
11. (Original post by MentalMath)
Is no one going to make a proper unofficial mark scheme?? Like the ones arsey made?
Arsey's probably too busy, and it wouldn't be worth it considering how few people do S3. In any case, you can go a few pages back and you will find an unofficial mark scheme. I think it wsa page 4?
12. (Original post by dhrumitvora)
perfect
sorry, but how did you work out the test stat?
13. (Original post by Xin Xang)
Arsey's probably too busy, and it wouldn't be worth it considering how few people do S3. In any case, you can go a few pages back and you will find an unofficial mark scheme. I think it wsa page 4?
More do S3 than M3

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14. Can someone tell whether or not I can still get an A star. I didn't do well in FP1 could have gotten as low as 70 and didn't do well in S3 could have gotten as low as 60, though neither test was difficult to be honest. I have S2,S4,FP2,FP3 left. Can I still achieve an A*?
15. (Original post by 13 1 20 8 42)
I did H0: U[0, 10] is a good model
H1: It isn't

And then Expected frequencies for each colour were

40, 30, 20, 10

I had a test statistic of around 13.something
v = 3, Critical region was like 11.something
Reject H0, U[0,10] not a good model
could you please tell me how u worked out the test statistic? please
16. (Original post by TabulaSmaragdina)
Can someone tell whether or not I can still get an A star. I didn't do well in FP1 could have gotten as low as 70 and didn't do well in S3 could have gotten as low as 60, though neither test was difficult to be honest. I have S2,S4,FP2,FP3 left. Can I still achieve an A*?
Yes
17. (Original post by TabulaSmaragdina)
Can someone tell whether or not I can still get an A star. I didn't do well in FP1 could have gotten as low as 70 and didn't do well in S3 could have gotten as low as 60, though neither test was difficult to be honest. I have S2,S4,FP2,FP3 left. Can I still achieve an A*?
I'm in a similar boat
60 will probably be around the A boundary, 70 certainly above that so you still have over 80% overall
And you need 90% across any 3 A2 modules (so 270/300 marks, not 90% in each module) as well as the overall 80%; all your remaining modules are A2
You are still well on course for an a*
18. Lol I meant % i.e. 60% and 70%.
(Original post by 13 1 20 8 42)
I'm in a similar boat
60 will probably be around the A boundary, 70 certainly above that so you still have over 80% overall
And you need 90% across any 3 A2 modules (so 270/300 marks, not 90% in each module) as well as the overall 80%; all your remaining modules are A2
You are still well on course for an a*
19. So would we get 0 marks for the table if we wrote 25 25 25 25 just marks for the conclusion, degrees of freedom and hypothesis?
None whatsoever for the table?
My teachers said we would only lose about 3-4 marks due to a final accuracy Mark and one or two for the expected frequencies, the test statistics should all follow through from our answers

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20. (Original post by varshanct95)
could you please tell me how u worked out the test statistic? please
Not quite sure if this is what you're asking; I did the usual sum of ((Oi - Ei)^2)/Ei; cannot remember what the individual Oi were

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