[AJCSShp]

I'm so dreading this exam! I just can't do stats!
In my D2 past papers I can get 72/73, but in stats I'm lucky if I scrap a B!
So what do people find the hardest in S2?

[matthew21]

I too believe that stats 2 is harder than other maths papers. Would anyone be able to exaplain the c.d.f on the january 2012 paper please, because I can't seen to be able to work it out in the given form :/

Thanks, and good luck to everyone

[HappyBun]

(Original post by matthew21)
I too believe that stats 2 is harder than other maths papers. Would anyone be able to exaplain the c.d.f on the january 2012 paper please, because I can't seen to be able to work it out in the given form :/

Thanks, and good luck to everyone

Are you referring to 6c)?

[5elsste]

I would advice everyone to try the June 2012 paper as I have in the past done pretty much all the papers and it is by far the hardest/weirdest!

[Miller693]

(Original post by 5elsste)
I would advice everyone to try the June 2012 paper as I have in the past done pretty much all the papers and it is by far the hardest/weirdest!

Yeah, think I'll give that paper a go tomorrow.

I'm guessing you mean January 2012, because you're definitely right; it is a strange one!

[magdaplaysbass]

(Original post by Miller693)
Yeah, think I'll give that paper a go tomorrow.

I'm guessing you mean January 2012, because you're definitely right; it is a strange one!

Yeah, the Jan 2012 paper has some weird questions in it; especially the discrete random variable one where you have to work out the probabilities Hopefully that means we'll get a really nice paper tomorrow

[5elsste]

(Original post by 5elsste)
I would advice everyone to try the June 2012 paper as I have in the past done pretty much all the papers and it is by far the hardest/weirdest!

No i meant the June 2011, sorry haha. The January 2012 is quite a hard paper but June 2011 is definitely harder. The grade boundaries for an A* was 62. The questions them selves aren't that bad its just they are in an unusual format. Have a look and you will realize what i mean.

[Pol]

Quick Question, Jan 2010, Question 4.a) Chi-squared.

On the group 19-30 the values are 2 and 14. And I thought you are meant to merge groups if they are lower than 5. But the mark scheme hasn't.

If you have one column lower than 5 and one higher than 5, do you not merge?
Thanks.

[magdaplaysbass]

(Original post by Pol)
Quick Question, Jan 2010, Question 4.a) Chi-squared.

On the group 19-30 the values are 2 and 14. And I thought you are meant to merge groups if they are lower than 5. But the mark scheme hasn't.

If you have one column lower than 5 and one higher than 5, do you not merge?
Thanks.

You only merge groups if the expected value, E, is less than 5. In this case, the observed value, O, is less than 5, but the expected value isn't; so there is no need to merge

[Pol]

(Original post by magdaplaysbass)
You only merge groups if the expected value, E, is less than 5. In this case, the observed value, O, is less than 5, but the expected value isn't; so there is no need to merge

Thank you! Shall remember that for tomorrow if it comes up

[Miyata]

Can someone help me please with question 7c on Jan09 paper. http://store.aqa.org.uk/qual/gceasa/...W-QP-JAN09.PDF
I understood up to F(4)-F(3), but why do you then divide that by F(4)? And what does | mean? Do I need to understand those probabilities in formulae booklet page 10 for it or no? Because I forgot them from s1, and we didn't go through them, and I don't even have s1 book anymore. I mean the ones like (AuB) = P(A) + P(B) - P(A upside down U B) ?

Just did another paper, similar thing came up, so looks like I need to know it. Can someone please explain it? Because Again I couldn't do the part with |, http://store.aqa.org.uk/qual/gce/pdf...W-QP-JUN10.PDF 6biii). I had 0.11, but didn't divide by 0.24.

Looks like it is some sort of formula? Please explain it someone!

[Skittles12]

(Original post by Miyata)
Can someone help me please with question 7c on Jan09 paper. http://store.aqa.org.uk/qual/gceasa/...W-QP-JAN09.PDF
I understood up to F(4)-F(3), but why do you then divide that by F(4)? And what does | mean? Do I need to understand those probabilities in formulae booklet page 10 for it or no? Because I forgot them from s1, and we didn't go through them, and I don't even have s1 book anymore. I mean the ones like (AuB) = P(A) + P(B) - P(A upside down U B) ?

Just did another paper, similar thing came up, so looks like I need to know it. Can someone please explain it? Because Again I couldn't do the part with |, http://store.aqa.org.uk/qual/gce/pdf...W-QP-JUN10.PDF 6biii). I had 0.11, but didn't divide by 0.24.

Looks like it is some sort of formula? Please explain it someone!

I also need help on this! I don't have my S1 textbook either

Would people recommend quickly going over the S1 course or not? Thanks

[magdaplaysbass]

(Original post by Miyata)
Can someone help me please with question 7c on Jan09 paper. http://store.aqa.org.uk/qual/gceasa/...W-QP-JAN09.PDF
I understood up to F(4)-F(3), but why do you then divide that by F(4)? And what does | mean? Do I need to understand those probabilities in formulae booklet page 10 for it or no? Because I forgot them from s1, and we didn't go through them, and I don't even have s1 book anymore. I mean the ones like (AuB) = P(A) + P(B) - P(A upside down U B) ?

Just did another paper, similar thing came up, so looks like I need to know it. Can someone please explain it? Because Again I couldn't do the part with |, http://store.aqa.org.uk/qual/gce/pdf...W-QP-JUN10.PDF 6biii). I had 0.11, but didn't divide by 0.24.

Looks like it is some sort of formula? Please explain it someone!

(Original post by Skittles12)
I also need help on this! I don't have my S1 textbook either

Would people recommend quickly going over the S1 course or not? Thanks

The | stands for 'given that'; so if you have P(A|B) it wants to know the probability of A occurring, given that B occurs.
So in the context of the question, it wants to know the probability of X being less than and equal to 3; given that X is less than and equal to 4.
So in other words, you need to work out the probability of X being between and equal to 3 and 4; and then divide that value by the probability of X being less than & equal to 4. So [F(4)- F(3)]/F(4)
It's quite hard to explain, but I hope that helped

[Pol]

Sorry for another question, But can someone please explain what standard error is?

E.g. http://store.aqa.org.uk/qual/gceasa/...W-QP-JAN09.PDF Question 5a iii) and 5a iv)

Thank you!

[Miyata]

(Original post by magdaplaysbass)
The | stands for 'given that'; so if you have P(A|B) it wants to know the probability of A occurring, given that B occurs.
So in the context of the question, it wants to know the probability of X being less than and equal to 3; given that X is less than and equal to 4.
So in other words, you need to work out the probability of X being between and equal to 3 and 4; and then divide that value by the probability of X being less than & equal to 4. So [F(4)- F(3)]/F(4)
It's quite hard to explain, but I hope that helped

Thanks, I noticed it after going through s1 probabilities half an hour ago that it is actually hard to explain xD And understand as well, but you just have to remember it.

(Original post by Pol)
Sorry for another question, But can someone please explain what standard error is?

E.g. http://store.aqa.org.uk/qual/gceasa/...W-QP-JAN09.PDF Question 5a iii) and 5a iv)

Thank you!

Standard error of the mean is just standard deviation (either s or o) divided by root n.
You don't know s.d. yet, but you know every other value for confidence interval. First look up t, which is 2.602
and then 75.5 + 2.602 * o/root16 = 80.35 =>> 2.602 * o/root16 = 4.85 ==> o/root16 = 1.86 (3s.f.)
and for second part it just asks you to find o^2. so o = 1.86*root16 and then square the number and you will get 55.6 to 3(s.f.).
I hope you will understand it, as I was rushing a bit. If you didn't get something let me know I will try explaining better.

[LGrosvenor101]

Hey guys! Just found this thread, whose looking forward to this tomorrow! Luckily I did AS Further Maths this year, so I can have my S1 and S2 modules swapped with my D1 and M1 modules I did in my AS, but I still want to do well :/ I'm just wondering if anyone has encountered any hard questions that would be worth tackling if possible? Thanks and good luck xD

[Lollyage]

Why didn't I take Decision 1 this year?

[Pol]

(Original post by Miyata)
Thanks, I noticed it after going through s1 probabilities half an hour ago that it is actually hard to explain xD And understand as well, but you just have to remember it.

Standard error of the mean is just standard deviation (either s or o) divided by root n.
You don't know s.d. yet, but you know every other value for confidence interval. First look up t, which is 2.602
and then 75.5 + 2.602 * o/root16 = 80.35 =>> 2.602 * o/root16 = 4.85 ==> o/root16 = 1.86 (3s.f.)
and for second part it just asks you to find o^2. so o = 1.86*root16 and then square the number and you will get 55.6 to 3(s.f.).
I hope you will understand it, as I was rushing a bit. If you didn't get something let me know I will try explaining better.

Thank you for your help.
A bit of S1 thrown in there...

[PhysicsGirl]

Hey, I don't know if this is helpful or not, but I always get confused as to whether to use n, or n-1, and I found this guide that the exam board publish as to which to use; http://store.aqa.org.uk/qual/pdf/AQA...1-GUIDANCE.PDF
Might be worth a look

[Miyata]

Can someone please explain 6c) june 2011? http://store.aqa.org.uk/qual/gce/pdf...W-QP-JUN11.PDF can't do it, don't understand what they even want. Everything was going so well, but 6c... -6 marks, and last question, -7 marks, ran out of time so and messed up...