S3 edexcel 22nd May 2019 Watch

Lucyodwyerx
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Anyone do this exam today, how did you find it?
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graciousgannon
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I did! Messed up big time on one of the 9 markers, found the paper overall quite difficult but I don’t think I did too badly.

How did you find it?
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Lucyodwyerx
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Better then last year I think 😂😂 but did have some hard bits in it ngl
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11thelman
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I only found the last question hard really, did anyone find part a) and c) the same?
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Josh9916
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i got part a and c on the last question the same
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ElbertAinstein
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I got a and c the same. Either edexcel made a error or im stupid.
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Lucyodwyerx
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I got A and C the same and C was worth 5 marks so I was baffled ?
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rakzee33
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For part C you had everything from the same population so you had to change W bar to (W1+W2+W3+W4)/4 and then find the expected value and variance. I got mu/2 and 87/4 sigma^2.
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Leniaeco
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What questions have come up? what was hard in it?
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ElbertAinstein
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Can you show how you got those answers. Question was W=4W1-3W2-Wbar
(Original post by rakzee33)
For part C you had everything from the same population so you had to change W bar to (W1+W2+W3+W4)/4 and then find the expected value and variance. I got mu/2 and 87/4 sigma^2.
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Leniaeco
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Write the questions and i am willing to provide a marking scheme in 2 hours
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rakzee33
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so if you convert Wbar into (W1+W2+W3+W4)/4 then you subtract 1/4*W1 from 4*W1 then you get 15/4*W1. I realise now that I made a mistake its meant to be mu=0. I subtracted W1/4 from 3 not -3. So you're meant to end up with 15/4*W1-13/4*W2-1/4*W3-1/4*W4. The expected value is then 0 and the variance will be 99/4*sigma^2
(Original post by ElbertAinstein)
Can you show how you got those answers. Question was W=4W1-3W2-Wbar
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Josh9916
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(Original post by rakzee33)
so if you convert Wbar into (W1+W2+W3+W4)/4 then you subtract 1/4*W1 from 4*W1 then you get 15/4*W1. I realise now that I made a mistake its meant to be mu=0. I subtracted W1/4 from 3 not -3. So you're meant to end up with 15/4*W1-13/4*W2-1/4*W3-1/4*W4. The expected value is then 0 and the variance will be 99/4*sigma^2
i got 101/4 sigma^2 for the variance because all the variances have to be added together
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Josh9916
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(Original post by Leniaeco)
Write the questions and i am willing to provide a marking scheme in 2 hours
my memory is foggy so feel free to correct me or add to this
Q1 idk how many marks
Q1a Spearman's rank question where I believe i got 17/20 maybe 3 marks
Q1b Typical Hypothesis testing question i think i rejected Ho 4 marks i think

Q2 Contingency Table 12 marks
i got v=(4-1)(2-1) = 3
can't remember the table sorry i know there were 100 males and 120 females and 220 total

Q3
part a was 3 marks You had to show P( W-mu > 20) = 0.001
also i think sigma was given to be 6. something

part b was to test the manager's claim about it being less than 500g


q4a asked i think how to stratify a population of dogs to a sample of 60
there like 2520 male dogs and 1680 female dogs i think i could be wrong
part b takes this from a different sample of dogs from the same population
says the manager claims that the mean weight loss of the female dogs is one more than the male dogs and i think it was a one sided test
i believe i accepted Ho althought i cant remember properly the weight of the dogs
my guess was female mean 2.1
male mean was 0.8
cant remember the amount of each and variances

q5 was the one about confidence intervals and you had to find it to 99% of the mean i believe
part b was something about finding the amount of 'n' needed if the width is at most 3cm to a 95% i think i could be wrong


q6 was the sector question and the probability of hitting that area of a sector is directly proportional to the angle of the sector
idk how many marks but it had A B C D for the sectors
i think b and c were 90° and D was 120° and A was 60°
i think the expected ones are 25 for B and C and 16.67 for A and 33.33 for D
observed i cant remember but C was 25

Q7 was the asking for the distribution of X and Y put together the
M= 4X1-3X2 -Ybar
and show that P( 4X1 < 3X2 +Ybar + sigma) = 0.5793

last bit said W=4W1 -3W2 -Wbar



this is from memory so again correct me if i make a mistake hope this helps
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