Edexcel S3 - Wednesday 25th May AM 2016

Yeah, nothing difficult, just the combination of boredom and doing it at 3 a.m that made dropped me ~4 marks from silly mistakes whereas the 6 questions in UK 15 were fun and enjoyable (towards the end, at least).

bruh i scored 70/75 within 30 mins on the ial and 59/75 on the normal.

I Made mistakes on qn 5 and then made silly mistakes like degree of freedom errors and that was it.

Hardest S3 papers? Have done June 2015, June 2015 IAL and June 2013R which were supposed to be hard, only tough question was 5d on June 2015, although that seems to be universally disliked by everyone on this thread

quick qn about the pmcc and srcc

do we find sxy and sxx of the ranks or the actual data? I assume ranks cos there would be no point of making it (a+b)/2 would it... so would i be right in saying we would do sxy etc with ranks???

Hardest S3 papers? Have done June 2015, June 2015 IAL and June 2013R which were supposed to be hard, only tough question was 5d on June 2015, although that seems to be universally disliked by everyone on this thread

Sounds like you've done them all. June 2013/4 (R) may be worth a go.

FWIW, I quite like Q5(d). So it's not universally disliked.



Yep!

Quick question, in what circumstances would you use the pmcc over the spearman rank and vice versa? Feel like I might have seen it be asked before

You'd use the pmcc in the rare cases when there are tied ranks and spearman in the very frequent case where the observed data isn't distributed bivariate normally or where there is non-linear correlation.

Anyone have a link to the 2015 IAL paper?

@Zacken

7.c
https://869d950bf149eefd5cd2652b400160ceb38ca5c7.googledrive.com/host/0B1ZiqBksUHNYVGVDMmVJYzVnRnc/June%202007%20QP%20-%20S3%20Edexcel.pdf

If you work it out by working out this: p(L-T<0.1) - p(L-T<-0.1)
You get a correct answer.
But if you do 2p(L-T<0.1)-1 you get it wrong?

I must've made a mistake somewhere, would like some help

@Zacken

7.c
https://869d950bf149eefd5cd2652b400160ceb38ca5c7.googledrive.com/host/0B1ZiqBksUHNYVGVDMmVJYzVnRnc/June%202007%20QP%20-%20S3%20Edexcel.pdf

If you work it out by working out this: p(L-T<0.1) - p(L-T<-0.1)
You get a correct answer.
But if you do 2p(L-T<0.1)-1 you get it wrong?

I must've made a mistake somewhere, would like some help

second that! what is the difference with that question, and this one 8a

https://869d950bf149eefd5cd2652b400160ceb38ca5c7.googledrive.com/host/0B1ZiqBksUHNYVGVDMmVJYzVnRnc/June%202013%20%28R%29%20QP%20-%20S3%20Edexcel.pdf

As above, see my post. In your question, the expected value of the difference is $0\,$ allowing us to use the symmetry and get to the expression, this is not true for the other question.

actually, you know what, the worst qns are the 1 or 2 markers that ask you random bullcrap as it is either right or wrong

eg/

The estimates of the standard error of the mean for the staff and for the children are 5.11 and 1.10 respectively.
(d) Comment on these values with reference to your answer to part (c) and give a reason for any differences