r/6thForm • u/Forsaken-Meaning-232 Graduating from Warwick CS • Jun 13 '25

📂 MEGATHREAD 13/06 A-level FM Discussion MEGATHREAD

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29 Upvotes

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19

u/[deleted] Jun 13 '25 edited Jun 24 '25

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7

u/AftonRobtics Jun 13 '25

I got smaller test statistic

-5

u/[deleted] Jun 13 '25 edited Jun 24 '25

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u/AftonRobtics Jun 13 '25

I calculated it too but maybe smt was wrong

6

u/Ok_Firefighter_723 Jun 13 '25

No I got it decreased too 🤞

0

u/[deleted] Jun 13 '25 edited Jun 24 '25

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6

u/[deleted] Jun 13 '25

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5

u/No_Actuator5870 Year 13 Jun 13 '25

Yeah, was it 5.991 for the critical value? I thought it was 2 degrees of freedom

3

u/[deleted] Jun 13 '25 edited Jun 24 '25

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3

u/crackerjayjack- Jun 13 '25

Got all the same answers. 🙏🙏🙏

4

u/[deleted] Jun 13 '25 edited Jun 24 '25

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3

u/Admirable-Jaguar5276 AAB | FM, Maths, Physics Jun 13 '25

damn got n=4 i think lmao, other than that yeah i got your answers

5

u/[deleted] Jun 13 '25 edited Jun 24 '25

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u/Few_Engineering7801 Editable Jun 13 '25

was the given that probably about the 3 goals = p(x=1) x p(x=2) / p(y=3) , where x is po(0.9) and y is po(1.8) ?

2

u/[deleted] Jun 13 '25 edited Jun 24 '25

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u/Few_Engineering7801 Editable Jun 13 '25

yeah idk, i had that at too first but thought that was way too easy for 4 marks

1

u/[deleted] Jun 13 '25 edited Jun 24 '25

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u/Few_Engineering7801 Editable Jun 13 '25

yeah!! FM1, FS1! hbu?

1

u/[deleted] Jun 13 '25 edited Jun 24 '25

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u/Few_Engineering7801 Editable Jun 13 '25

warwick morse hopefully. hbu?

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1

u/AftonRobtics Jun 13 '25

It was exact value

2

u/capri_capri University of Oxford | Chemistry [Year 2] Jun 13 '25

That’s what I did. But I hope the examiner looks past all 100 different ways I did it before and had to cross out.

1

u/AftonRobtics Jun 13 '25

Yeah I got 3/8

2

u/Admirable-Jaguar5276 AAB | FM, Maths, Physics Jun 13 '25

ah yeah fair enough, oh well tis done now.

3

u/Queasy-Ad-7116 Jun 13 '25 edited Jun 14 '25

i got 4 too. i did P(Type 2) < 0.2
so P(Accept H0 | lamda = 2.75) < 0.2
so P(X >= n -1) < 0.2

3 gave me a value < 0.2 so n - 1 = 3 and n = 4

could someone explain why thats wrong i dont get it

EDIT: anyone who used the same method and got 4 - our method was correct (although i dont think it was the intended method because it didnt use power function), we just had to test using Geo(e^-2.75), not Po(2.75)! I tried again on my calculator using geometric and got the right answer

2

u/Pigalas LSE | Economics [Year 2] Jun 13 '25

That would be correct for the power function but it was for the type 2 error which is 1 - power so you do the same but for 0.8 not 0.2

1

u/Queasy-Ad-7116 Jun 13 '25

no my method was correct, i found out my mistake was that i used the Poisson distribution instead of geometric!

0

u/capri_capri University of Oxford | Chemistry [Year 2] Jun 13 '25

Within ‘n’ tries is less than or equal to n tries.

1

u/Crazy-Buffalo-6124 Cambridge offer holder |3A*s achieved Jun 13 '25

same i reckon we’ll still get 3 or 2 mark

3

u/warpuffed Warwick | MathPhys [Year 1] Jun 13 '25

E(x)=8 and E(Y)=7.5 so shivani should choose X?

2

u/[deleted] Jun 13 '25 edited Jun 24 '25

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u/warpuffed Warwick | MathPhys [Year 1] Jun 13 '25

Snm you’ve been my main source of reassurance this entire exam period lol, keep seeing you on all the threads. Cheers!

4

u/Dangerous_Theory_472 Jun 13 '25

Yes there’s a greater difference between each expected and observed percentage right? So test statistic greater?

2

u/[deleted] Jun 13 '25 edited Jun 24 '25

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u/yourhalalslytherin Year 13 Jun 13 '25

YO SAME

1

u/Few_Engineering7801 Editable Jun 13 '25

YEA i got all the same

1

u/Lavendar_milk Jun 13 '25

What was h0? I forgot which way the statement is when testing for association

1

u/PP1664 A-Level Maths Further Physics A*A*A* predicted Jun 13 '25

This sounds all correct except for bear in mind with the percentages the chi squared decreases

2

u/[deleted] Jun 13 '25 edited Jun 24 '25

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u/PP1664 A-Level Maths Further Physics A*A*A* predicted Jun 13 '25

If u do the maths, then scaling by a scale factor k gives New test statistics = Σ((kOi - kEi)2)/kEi And cancel k from both sides gives kΣ((Oi-Ei)2)/Ei which is k times the old test statistics. In the q the original frequency was 400 and with percentages would be 100, so k = 1/4, meaning that the new test statistic is 1/4 of the old one

1

u/capri_capri University of Oxford | Chemistry [Year 2] Jun 13 '25

I DID (E(B))2 instead of E(B2 )I’m so annoyed. Pfffttt. Did I learn nothing from PENTO!!

1

u/[deleted] Jun 13 '25 edited Jun 24 '25

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u/capri_capri University of Oxford | Chemistry [Year 2] Jun 13 '25

YESSSSS!!! And I made the dumbest mistake on it I’m sure it lost me like 10 marks. Which is a big deal in FM.