S4 A-Level Maths Edexcel June 26 2018 Unofficial Markscheme

Original post by Pepperpeople

I got two ranges for m. As it was two tailed I think you had to take into account the positive and negative tails

Yes, you did have to find two ranges for m, but then if you bring them together, it will simplify to just one range (with two tails). Look for the overlap of the two ranges.

Reply 23

Redcoats

10

Original post by mupsman2312

Yes, you did have to find two ranges for m, but then if you bring them together, it will simplify to just one range (with two tails). Look for the overlap of the two ranges.

The question said find the 'ranges' (plural). Would that mean anything here?

Reply 24

Original post by Redcoats

The question said find the 'ranges' (plural). Would that mean anything here?

Well, we all would have put both ranges in our working, so they should see that anyway. Just giving it as one range is only a simplification of these two ranges combined. It shouldn't matter too much either way.

Reply 25

Pepperpeople

6

Original post by Redcoats

The question said find the 'ranges' (plural). Would that mean anything here?

I know I definitely got one of the ranges wrong anyway but the way the question was phrased made me think it would be two separate ones

(edited 5 years ago)

Reply 26

Redcoats

10

Original post by mupsman2312

Well, we all would have put both ranges in our working, so they should see that anyway. Just giving it as one range is only a simplification of these two ranges combined.

Agreed, you'll still get the full marks. I was wondering if the simplification was necessary and if one would be penalised for merely giving two separate ranges. Thoughts?

Reply 27

Original post by Redcoats

Agreed, you'll still get the full marks. I was wondering if the simplification was necessary and if one would be penalised for merely giving two separate ranges. Thoughts?

It may not have been necessary, so don't worry about it. If they're REALLY fussy, then you might drop one mark, but the main part of the question would just have been to find the two ranges, so they shouldn't mind too much about how you write them.

Reply 28

Original post by Nyathigiz

Ye

Because it was consistent unlike s2, and because for s1 n has to be at least 2 and so was smaller also? (S2 had 1/11 as its fraction of theta)

Reply 29

Wtf did we have to do for the last 2 parts of the glue question? I didn't manage to do much with those questions. I wrote no, I tried finding the new s^2 and mean of the glue that had the errors. Also, what did everyone do for the last question, for a and b, and for showing the minimum variance was a given fraction. I think my a's and b's (had 2 values for each were 1 and -1 and the other set were 2 fractions, 11 was in the number)

Reply 30

Original post by Evil Homer

If you guys want to set up an unofficial markscheme I could promote it around the site and get it filled in as soon as possible :smile:

Hope the exams went okay today! :biggrin:

Please

Reply 31

Guys do you think 55/75 would be an A this year ?

Reply 32

So hopeful that I would get an A* this year after FP2 and S3 but this S4 exam dashed all hopes . What can you do that’s life I suppose .

Reply 33

My ranges were m less than 0.37 and m is greater or equal to 0.04 and some long decimals after that.

Reply 34

Original post by mupsman2312

These are some of the answers which I remember getting:

P(Type I error) = 0.05
Minimum value of n is 35

E(X) = (4/3)theta
E(X^2) = 2theta^2 and Var(X) = (2/9)theta^2
Var(S1) = (theta^2)/(8n)
a = 6/11 and b = 9/11 (4a + b = 3)
S1 is the better estimator

Differences are normally distributed
0.0490 <= m <= 0.3774

Confidence interval for mean: [47.93, 56.07]
Confidence interval for sd: [3.57, 10.14]
Don't change to Zesty, as 3.57 < 5.5 (< 10.14) - I.e. Jeremiah can't be sure that sigma < 5.5

F-test: 4.53 < 5.19 ==> not significant
Pooled estimate of variance = 0.24698...
t-test: 2.825 > 1.833 ==> significant

Q1: 3.333 > 2.821 ==> significant

Can anyone please confirm? Sorry for going in such a weird - almost reverse - order!

YESSS. THIS IS ALL GOOD. Although I think I got slightly (Ever so slightly different a's and b's, i have that same equation, but also a quadratic for a and b) there was an 11 in there though.

Reply 35

Original post by Lifeofwind88

Guys do you think 55/75 would be an A this year ?

Unlikely to be that low because of the calibre of students who do S4, but I hadn't gotten less than like 68/75 in all the past papers I did and I'm pretty sure I lost around 7-8 marks. I'm thinking this gives me a comfortable A* though. Perhaps 61 for an A?

Reply 36

Original post by dugdg

Unlikely to be that low because of the calibre of students who do S4, but I hadn't gotten less than like 68/75 in all the past papers I did and I'm pretty sure I lost around 7-8 marks. I'm thinking this gives me a comfortable A* though. Perhaps 61 for an A?

As long as I get into UCL I’m happy , best of luck to you man as well

Reply 37

EdwardG

@mupsman2312 There were two separate ranges, and they couldn't be combined. a < m < b and c < m < d where c > b, in other words, there's a bunch of values there in between which m can not be.

Would you mind showing me how you worked out the value for n? I got a really weird answer.

Reply 38

ericaliu99

4

Original post by CornOnTheCog

I think I got like 35?

me too

Reply 39