Edexcel S2 Revision Thread

reem02

how did you find the paper?

really wordy lol - what was with the gazillion definitions?!

Reply 186

reem02

I got 1/6 =S thats the only q in the paper i wasnt sure about other than that it was quite good.
what did you get?

Did you forget to do both ends? (yeah it was one of those cumulative dist questions)

I did too, fml :frown:

I reckon I'll get 2 marks for finding the height, finding 1/6th, and then multiplying them, so its not THAT bad.

Also I ballsed up the last part of the last question, I never got down to finding what 'a' and 'k' were (I gto half way but I ran out of time), so I just guessed what I thought the f(x) graph would look like and said the mode was 1 (I've got like a 1 in 4 chance of it being right :rolleyes:

), but my mate said it was 2, so :s-smilie:

Reply 187

Aliison

Yeah, the questions where they asked you to state the hypothesis were both significant I think.

And the one where you had to find the critical region, then they gave you 8 as the actual value, that was insignificant because it fell outside of the critical region.

Sounds reasonably familiar :smile:

The critical regions for the 8 were like X<6 or X>?16 something like that anyway I think!

Reply 188

TylerDurden

2

cari

2/3 for question 3 because for the longest side to be >6, either X<4 or X>6 = 1/2 + 1/6 = 2/3 :smile:

Its actually a half, because P(X<4) = 3*1/6.

It was uniformly distributed between [1,7], not [0,6] so everything moves up.
Hopefully we should get 3 method marks as it was a 5 mark question.

Reply 189

cari

really wordy lol - what was with the gazillion definitions?!

Haha, those were the only definitions I actually new.

I got my mum to test me literally an hour before the exam - thats the only reason I knew them :biggrin:

Reply 190

916-CALL-TURK

Did you forget to do both ends? (yeah it was one of those cumulative dist questions)

I did too, fml :frown:

I reckon I'll get 2 marks for finding the height, finding 1/6th, and then multiplying them, so its not THAT bad.

Also I ballsed up the last part of the last question, I never got down to finding what 'a' and 'k' were (I gto half way but I ran out of time), so I just guessed what I thought the f(x) graph would look like and said the mode was 1 (I've got like a 1 in 4 chance of it being right :rolleyes:

), but my mate said it was 2, so :s-smilie:

I had the mode as 2/9 i think because k=1/9 :s-smilie:

Reply 191

TylerDurden

Its actually a half, because P(X<4) = 3*1/6.

It was uniformly distributed between [1,7], not [0,6] so everything moves up.
Hopefully we should get 3 method marks as it was a 5 mark question.

but you also need the possibility that X>6 surely? which is 1/6, 1/6 + 1/2 = 2/3 :s-smilie:

Reply 192

So question 3 was:

A rectangle has a perimeter of 20. One side has a length with a cumulative uniform distribution between 1 and 7. Find the probability that the longer side is greater than 6 cm

Reply 193

TylerDurden

2

cari

but you also need the possibility that X>6 surely? which is 1/6, 1/6 + 1/2 = 2/3 :s-smilie:

It's uniformly distributed between [1,7] so height is 1/6.
P(X<4) = (4-1)*1/6. It's 4-1 as lower limit is 1, not 0.

If you draw it out it makes sense. :frown:

Reply 194

reem02

cari

i think the answer was 2/3 as for the longest side to be >6, either X>6 or X<4 (so the other side >6) = 1/2 + 1/6 = 2/3 :smile:

Hope that helps

Oh crap i forgot x<4 i got it thnx :smile:

well i get few marks for finding half the ansr lol

Reply 195

TylerDurden

It's uniformly distributed between [1,7] so height is 1/6.
P(X<4) = (4-1)*1/6. It's 4-1 as lower limit is 1, not 0.

If you draw it out it makes sense. :frown:

Yeah I get that, so that is where my "1/2" comes from, but you're forgetting the situation when X>6 which the probability is 1/6, so you have to add this to the "1/2" giving you 2/3 surely? :s-smilie:

Reply 196

cari

but you also need the possibility that X>6 surely? which is 1/6, 1/6 + 1/2 = 2/3 :s-smilie:

1/6 + 1/6 +1/2 is NOT 2/3 :rolleyes:

My mate got 2/3 from 1/6 + 1/2 as 1/6 was the probability if it were represented by a CUD, and the 1/2 was the probability if it were not represented by a CUD (I still dont get that).

Alrighty. I'm off :p:

Ridiculous amounts of CHEM4/BIOL4/C4 to revise over the next 6 days :eek3:

Reply 197

reem02

916-CALL-TURK

Did you forget to do both ends? (yeah it was one of those cumulative dist questions)

I did too, fml :frown:

I reckon I'll get 2 marks for finding the height, finding 1/6th, and then multiplying them, so its not THAT bad.

Also I ballsed up the last part of the last question, I never got down to finding what 'a' and 'k' were (I gto half way but I ran out of time), so I just guessed what I thought the f(x) graph would look like and said the mode was 1 (I've got like a 1 in 4 chance of it being right :rolleyes:

), but my mate said it was 2, so :s-smilie:

I got mode as 2
K as 1/9

To find a it took me 2 tries. but i did manage to get a 4.

Reply 198

reem02

cari

I had the mode as 2/9 i think because k=1/9 :s-smilie:

mode was just 2 for me.... how did you get 2/9?

Reply 199