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OCR S3 (non-mei) June 28 2017

How'd you guys think it went? Personally I think it was great, but the last question was tricky...
Reply 1
Avatar for saba123
saba123
What were some answers/values you can remember. Thought it was pretty tricky
The last question was almost copied word for word from an S3 textbook

FullSizeRender.jpg
Reply 3
Avatar for CC21231
CC21231
12
Original post by fuzzball909
The last question was almost copied word for word from an S3 textbook

FullSizeRender.jpg


That's not fair I definitely didn't get that
Reply 4
Avatar for m4thsisg8
m4thsisg8
OP
1
Original post by saba123
What were some answers/values you can remember. Thought it was pretty tricky


sadly, I can't remember any values :frown: but if you tell me some of yours then I might be able to remember :biggrin:
Reply 5
Avatar for m4thsisg8
m4thsisg8
OP
1
Original post by fuzzball909
The last question was almost copied word for word from an S3 textbook

FullSizeRender.jpg


No way... Hahaha! I got the pdf right :smile: I think I got my limits wrong though.
Reply 6
Avatar for saba123
saba123
What were the limits? I got 4f/3 and 3f/2 I think. Not sure that was right. Also got PDF in a weird form.
From my answers I remember:
Probability for Z=15 was 0.0303 or something
0.66 was the test value for the proportions Q
3.66 for normal chi squared fitting
For paired t test test value was like 2.1 something
Pretty tough paper for me, think I dropped between 6 and 10 marks
Reply 7
Avatar for dg16023
dg16023
3
Went great but think overall the grade boundaries won't be high. Did you guys do three constraints for when seeing if the Normal was a good model?
Reply 8
Avatar for m4thsisg8
m4thsisg8
OP
1
Original post by saba123
What were the limits? I got 4f/3 and 3f/2 I think. Not sure that was right. Also got PDF in a weird form.
From my answers I remember:
Probability for Z=15 was 0.0303 or something
0.66 was the test value for the proportions Q
3.66 for normal chi squared fitting
For paired t test test value was like 2.1 something
Pretty tough paper for me, think I dropped between 6 and 10 marks


I accidentally approximated to normal, for Z=15 and I got 0.0287 I think yours is right though.
Same although I got -0.66 since I subtracted the other way around.
Same I think
For paired t-test I think my mean value of difference was 12.5 and the variance was like 296.2777...
and that gave me a test value of 2.296
Answers I can remember:
confidence interval for first question: [5.355, 8.645]
paired t test question: i got variance estimate ≈ 296 and T = 2.30 (i think H0 was rejected)
for the chi-squared normal distribution question i got chi squared ≈ 3.67
for Z = 4X + 5Y, X~Po(2) and Y~Po(3) i got P(Z = 15) = 0.0303
For the 8 apples question i think i got T = -0.662 (i think H0 was accepted)
Last question i got g(v) = f/(v-f)^2 for (4/3)f <= v <= (3/2)f
Reply 10
Avatar for m4thsisg8
m4thsisg8
OP
1
Original post by dg16023
Went great but think overall the grade boundaries won't be high. Did you guys do three constraints for when seeing if the Normal was a good model?


Yeah I made it to be 2 degrees of freedom for the test
Reply 11
Avatar for dg16023
dg16023
3
Original post by m4thsisg8
Yeah I made it to be 2 degrees of freedom for the test


I can't remember ν exactly, 2 sounds familiar, classes had to be grouped either side.

Another detail was the Yates' correction for the 2*2.
For the last question I found the cumulative and probability distribution function for U and then tried playing around with V. How many marks would I get for this?
Reply 13
Avatar for sammy183
sammy183
Grade boundaries?
Is there an unofficial mark scheme?
Reply 15
Avatar for dg16023
dg16023
3
Original post by sammy183
Grade boundaries?


not particularly high
Original post by m4thsisg8
I accidentally approximated to normal, for Z=15 and I got 0.0287 I think yours is right though.
Same although I got -0.66 since I subtracted the other way around.
Same I think
For paired t-test I think my mean value of difference was 12.5 and the variance was like 296.2777...
and that gave me a test value of 2.296


I got 0.0287 as well hopefully we will get some marks
Original post by Bobby21231
I got 0.0287 as well hopefully we will get some marks


I did that too I wasn't sure what else to do😂

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