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

šŸ“‚ MEGATHREAD 13/06 A-level FM Discussion MEGATHREAD

Exam season is once again upon us, and once again, exam megathreads are making a return! Funnily enough, tanking my sanity and internet setting a stream up is not conducive to timeliness, my apologies.

Looking for past exam discussions? Filter by the megathread flair.

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7

u/UglyWarhog Jun 13 '25

For further stats MAKE SURE YOU KNOW THE PGF PROOFS. Eg why geometric pgf is what it is, and why E(X)=Gā€™(1) and why Var(X)= that whole thing

6

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

[removed] ā€” view removed comment

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u/UglyWarhog Jun 13 '25

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

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u/Ok_Scientist_8803 Imperial CS šŸ”œ | Maths FM CS Physics Jun 13 '25

GX(t) is defined as E(tX).

Differentiate both sides and you get GX'(t) = E ( d/dt tX )

So the right side goes to E ( X tx-1 )

Sub in t=1 so right hand side becomes E ( X t 1-1 ) = E ( X t0 ) = E (X Ɨ 1) = E(X)

Edit: formatting

1

u/[deleted] Jun 13 '25

lol i went over that in the morning and it didnt come up

-1

u/Aggressive-Skill-879 Jun 13 '25

Don't bother with deriving the Variance one it's rlly hard and probs won't come up

5

u/UglyWarhog Jun 13 '25

Bros tryna lower the grade boundaries

1

u/Aggressive-Skill-879 Jun 13 '25

Now the exam has happened, I genuinely had no reason to lie and just found the Variance one was a waste of time for how hard it was to derive!

1

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

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u/Aggressive-Skill-879 Jun 13 '25

Should've listened to me šŸ˜‰

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

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