Year 12s: what will be the first way you research your future options? >>

Ocr mei s3 june 2015

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I got 90 for n and the last question pissed me off I tried everything but still got the smallest of probabilities. You know you're doing something wrong when you get 0.000000000000000000000000000008 or similarly ridiculous

Reply 21

Paradoxic

Original post by chizz1889

I will do an unofficial mark scheme after I've drove home if u guys want!

Sound good man

Reply 22

lebanon95

Original post by chizz1889

Had a sudden realisation which saved me on the last question, got it to be distributed ~N(0,9.75). I got the sample size to be 90. What about you?

Spill the beans mate

Reply 23

Dan205

For the last question for the variance I did 1/4 and 1/9 of the variances in order to get the "mean" variance?

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Reply 24

mathsexam2013

Last question i messed up, got n=90
wat did evry1 get for the tests

Reply 25

mathsexam2013

got 0.77 something for another part of the last qs

Reply 26

chizz1889

Here's my answers that I can remember :
1. a) i) cant remember the ratios but it was a simple question just make sure they add up to 500 afterwards
ii) I put by gender and also by year group
iii) adv of staratified sample is that the sample contains data from each strata in the same ratio as it exists in the population so is more representative.
b) i)the underlying distribution is unknown.
ii) the population must be symmetrically distributed about the population median.
iii) W-=21, critical value =17. Not significant.
2.i) integrated function between 0&5 =1 k=2/35
ii) show that
iii) make sure you group 0<x<2 chi squared =7.552 CV = 6.251 , significant etc
3 degrees of freedom, result was significant etc
iv) significantly less than expected in 0<x<2. Significantly more than expected in 3<x<4.
3. i) 5% chance of rejecting H0 when it is true.
ii) sample is random, differences must have underlying normally distributed population. (Variance is unknown?)
iii) CV & TS were 2.something, TS>CV, result was significant etc
iv) 10% t9 = 1.833 d mean (4.93 +- 1.833*6.3105/root10)
4.i) in repeated samples , 95% of confidence interval constructed in the same way will contain the true population mean
ii) I got n=90 and mean = 46.2999 (46.3)
iii) X~N(86.1,25.9) then did less than 90 - 0.7783
iv) Y~N(3.5,25.9) then did more than 5 - 0.3841
v) G~N(0,9.75) then did more than 3 - 0.1683

BAR ANY ERRORS, IT's COMPLETE :biggrin:

(edited 8 years ago)

Reply 27

chizz1889

Original post by Dan205

For the last question for the variance I did 1/4 and 1/9 of the variances in order to get the "mean" variance?

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Close it was 1/2 and 1/3. Will post a pic in a second why

Reply 28

Dan205

Original post by chizz1889

Close it was 1/2 and 1/3. Will post a pic in a second why

Okay cheers :smile:

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Reply 29

chizz1889

Original post by Dan205

For the last question for the variance I did 1/4 and 1/9 of the variances in order to get the "mean" variance?

Posted from TSR Mobile

Reply 30

Dan205

Original post by chizz1889

Yeah I got that! :smile:

cause 1/9 is 1/3 squared and 1/4 is 1/2 squared :tongue:

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Reply 31

AndyChow

Anyone have idea of confidence interval? Did the question ask for differences or just one row?

Reply 32

chizz1889

Original post by Dan205

Yeah I got that! :smile:

cause 1/9 is 1/3 squared and 1/4 is 1/2 squared :tongue:

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Yeah then you had to add the variances of each so it ends up being 1/2 & 1/3 😀

Reply 33

mathsexam2013

Original post by chizz1889

Here's my answers that I can remember :
1. a) i) CANT REMEMBER
ii) CANT REMEMBER
b) i) there's a significant difference after the drive so this test eliminates these differences (I had no idea)
ii) the population must be symmetrically distributed about the population median.
iii) W-=21, critical value =17. Not significant.
2.i) integrated function between 0&5 =1 k=2/35
ii) show that
iii) make sure you group 0<x<2
3 degrees of freedom, result was significant etc
iv) significantly less than expected in 0<x<2. Significantly more than expected in 3<x<4.
3. i) 5% chance of rejecting H0 when it is true.
ii) variance must be unkwown, sample is small, differences must have underlying normally distributed population
iii) result was significant etc
iv) CANT REMEMBER
4.i) in repeated samples , 95% of confidence interval constructed in the same way will contain the true population mean
ii) I got n=90 and mean = 46.2999
iii) X~N(86.1,25.9) then did less than 90
iv) Y~N(3.5,25.9) then did more than 5
v) G~N(0,9.75) then did more than 3

Feel free to help by adding new to the parts I can't remember or make corrections ☺️

for first qs i think one of the numbers i got was 118 and another was 124
for the second question strata like gender, rural/urban, type of house
for chi squared got around 7.something for test statistic and 6. soemthing for critical value
for qs 3 2.262 was crit value i think and test statisticc was a bit bigger 2.7? cant remeber, for CI use k=1.833

for qs4 could you please explain last part, would appreciate it