How was Edexcel S2?

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Leekey

You only HAD to use the continuity correction once but if you decided to use the normal instead of the poisson for an earlier question then you should have done it twice.

I used the poission :smile:

Yay thank you

Reply 101

Mysticmin

Is it just me, or is everyone else thinking the grade boundaries are going to shoot up for S2 this year...

Reply 102

Leekey

Mysticmin

Is it just me, or is everyone else thinking the grade boundaries are going to shoot up for S2 this year...

Don't say that, I'll lose all confidence in getting that B. :biggrin:

Reply 103

Mysticmin

Leekey

Don't say that, I'll lose all confidence in getting that B. :biggrin:

Ha ha, no worries, with that paper everyone will pull off over 90%, and edexcel will kick themselves are being unable to discern which people they'll chuck over the A grade boundary.

Reply 104

John Porcella

DaKe

yea that's rite. The median(1.4) was greater then the mean (1.21111? i think) therefore negative skew

I left the answer as 109/90, which my calculator assures me now is 1.2111etc..

I thought that the skew was negative. I got stuck on this question for a while and ended up drawing a sketch to see what was going on. The mode was way over to the right with the mean somewhere to the left, so the tail was pointing towards the negative numbers, so hence negatively skewed.

John

Reply 105

sideshowbob

Wasnt 2)a) 0.74 rather than 0.54 as many people have said. (2.7+1)/5 = 0.74

Was the one approximated by the normal distribution 0.1847?

Reply 106

Leekey

sideshowbob

Wasnt 2)a) 0.74 rather than 0.54 as many people have said. (2.7+1)/5 = 0.74

Was the one approximated by the normal distribution 0.1847?

It was indeed, because it existed between -1 and 4 (I think) and for P(X<2.7) you must factor in the negative bit of the distribution to five 3.7/5 which is 0.74.

0.1847 looks vaguely familiar but I cant remember to be honest.

Reply 107

RussianDude

sideshowbob

Wasnt 2)a) 0.74 rather than 0.54 as many people have said. (2.7+1)/5 = 0.74

Was the one approximated by the normal distribution 0.1847?

i think it should be 1/5 * 2.7 = 0.54

Reply 108

RussianDude

5)b) 0.991
c) 0.9473

anyone else got ^?

Reply 109

sideshowbob

P(Z>= (21.5 – 17.5)/(Rt 17.5))

= 1- P(Z<= 0.89)

= 0.1847

Agree?

i agree

sideshowbob

P(Z>= (21.5 – 17.5)/(Rt 17.5))

= 1- P(Z<= 0.89)

= 0.1847

Agree?

Yes, I do remember that one now. I definitely remember the 0.89 bit and the answer looks very familiar.

Reply 112

Asha

anyone got the exam paper?

always asked, yet never answered :frown:

Reply 113

lgs98jonee

Leekey

Usually to works like....

-Correct hypothesis
-Correct interpretation of distribution
-Correct probability
-Correct n value
-Correct comparison with sig level
-Correct in rejecting / not rejecting H0
-Correct in interpreting result of rejecting / not rejecting

say i got n value wrong, did correct follow up method but as a result my interpretation was wrong (soley becos of wrong n value) how many marks out of last 4 do u think i might get?

Reply 114

DaKe

RussianDude

i think it should be 1/5 * 2.7 = 0.54

Nah i dont think so mate, cos i did that first but then realised that its u have to do it for -1<=x<=2.7, therefore the difference is 3.7 and so u do 1/5*3.7 which gives 0.74 and not 0.54

Reply 115

RussianDude

How many marks would i loose if i forgot about the interpolation in q 6)d)?

Reply 116

clare_m

DaKe

Nah i dont think so mate, cos i did that first but then realised that its u have to do it for -1<=x<=2.7, therefore the difference is 3.7 and so u do 1/5*3.7 which gives 0.74 and not 0.54

my god, why do people make it sooo difficult, ure find the area of the rectangle so length of base x length of height....so (2.7 - -1) x 1/5 = 0.74
ITS OBVIOUS
...lets stop discussing it....

Reply 117

clare_m

RussianDude

How many marks would i loose if i forgot about the interpolation in q 6)d)?

interpolation? do u mean the contingency thing? if so u lose one mark for not showing u subtracted 0.5 and then one mark for the actual answer. otherwise it SHOULD be method marks you pick up - going from past paper experience