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Author Topic: S1 and S2 DOUBTS HERE!!!!  (Read 63368 times)

Offline mdwael

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Re: S1 DOUBTS HERE!!!!
« Reply #195 on: May 19, 2011, 08:11:47 pm »
okay I have something which I want to make clear of.  When you code data.. Product moment correlation is not affected, Variance and standard deviation are only affected when you multiply and divide and Mean is affected by everything. Am I right?
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Offline xMilishax

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Re: S1 DOUBTS HERE!!!!
« Reply #196 on: May 19, 2011, 08:57:05 pm »
Can someone please explain Q7(a) in Jan 2011 S1 paper?

Thanks.  :)
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Offline xMilishax

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Re: S1 DOUBTS HERE!!!!
« Reply #197 on: May 19, 2011, 09:22:46 pm »
I got it. LOL  :P
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Offline Master_Key

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Re: S1 DOUBTS HERE!!!!
« Reply #198 on: May 24, 2011, 02:04:19 pm »
CIE

9709_s10_qp_62

Q 7 (ii).

I just want to know any short method, i have got the answer but with a way too long method.
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Offline Ghost Of Highbury

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Re: S1 DOUBTS HERE!!!!
« Reply #199 on: May 24, 2011, 02:37:33 pm »
Quote from: Master_Key on May 24, 2011, 02:04:19 pm
CIE

9709_s10_qp_62

Q 7 (ii).

I just want to know any short method, i have got the answer but with a way too long method.

as the markscheme suggests, its simple. 

The no. of ways the pink card is not next to the green card = Total no. of ways - (the no. of ways the green card and the pink are together)

The no. of ways the pink and green are together...
There is a very neat trick to find this, it's in there in the CIE S1 book
U consider the 2 cards as a unit, and permute them with the other 7

Like this [pink, green] + 7 others... = total 8 (regarding the pink, green as one unit)
 
The permutation = 2*8!

Subtract this from 9! and u have ur answer

9!-(2*8!)
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Offline Master_Key

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Re: S1 DOUBTS HERE!!!!
« Reply #200 on: May 24, 2011, 02:41:04 pm »
Quote from: Ghost Of Highbury~ on May 24, 2011, 02:37:33 pm
as the markscheme suggests, its simple.  

The no. of ways the pink card is not next to the green card = Total no. of ways - (the no. of ways the green card and the pink are together)

The no. of ways the pink and green are together...
There is a very neat trick to find this, it's in there in the CIE S1 book
U consider the 2 cards as a unit, and permute them with the other 7

Like this [pink, green] + 7 others... = total 8 (regarding the pink, green as one unit)
 
The permutation = 2*8!

Subtract this from 9! and u have ur answer

9!-(2*8!)

Thank you. So for combinations also I think this would be easier. +rep(I have to wait 114 minutes)
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Offline SkyPilotage

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Re: S1 DOUBTS HERE!!!!
« Reply #201 on: May 24, 2011, 05:36:01 pm »
Do we need to know the 52 cards pack!?
Do we need to know how to derive the formulas of vairance and standard deviations in sets of date or binomial distributions or why?!?!
Thanks...
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Offline Ghost Of Highbury

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Re: S1 DOUBTS HERE!!!!
« Reply #202 on: May 24, 2011, 07:19:56 pm »
Quote from: SkyPilotage on May 24, 2011, 05:36:01 pm
Do we need to know the 52 cards pack!?
Do we need to know how to derive the formulas of vairance and standard deviations in sets of date or binomial distributions or why?!?!
Thanks...

52 pack cards - yes. (No jokers ofcourse)

Derive the formulas for variance and s.d? Nah
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Offline SkyPilotage

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Re: S1 DOUBTS HERE!!!!
« Reply #203 on: May 24, 2011, 07:35:55 pm »
Quote from: Ghost Of Highbury~ on May 24, 2011, 07:19:56 pm
52 pack cards - yes. (No jokers ofcourse)

Derive the formulas for variance and s.d? Nah
can you tell me the 52 card pack?
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Offline Ghost Of Highbury

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Re: S1 DOUBTS HERE!!!!
« Reply #204 on: May 24, 2011, 07:39:05 pm »
Quote from: SkyPilotage on May 24, 2011, 07:35:55 pm
can you tell me the 52 card pack?

Erm, ok sure. 52 cards. 26 red and 26 black. four As, four 2s, four 3s, four 4s................four 10's, four jacks, four queens, four kings.

13 spades, 13 hearts, 13 diamonds and 13 clubs.

Find attached image. Source : wiki
« Last Edit: May 24, 2011, 07:40:42 pm by Ghost Of Highbury~ »
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Offline dj_dead

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Re: S1 DOUBTS HERE!!!!
« Reply #205 on: May 25, 2011, 08:06:39 am »
june 2008 paper 6 q5 part ii


when we get phi(t) = 0.7389
then how come the next step is
phi (t) = phi (0.64)


where did 0.64 come from? =S
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Offline EMO123

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Re: S1 DOUBTS HERE!!!!
« Reply #206 on: May 25, 2011, 08:44:24 am »
Quote from: dj_dead on May 25, 2011, 08:06:39 am
june 2008 paper 6 q5 part ii


when we get phi(t) = 0.7389
then how come the next step is
phi (t) = phi (0.64)


where did 0.64 come from? =S
I got that by the method given bellow

Take the medians of the time spent intervals
i.e. :- 0.3, 0.8, 1.55, 2.55, 3.8
now use the formula sigma fx
                            --------
                             sigma f
sigma fx = 3.3+12+27.9+76.5+79.8 = 199.5
sigma f = 11+15+18+30+21=95

:. 199.5/95=2.1
the mean is 2.1 hours
hope it helps
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Offline Ghost Of Highbury

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Re: S1 DOUBTS HERE!!!!
« Reply #207 on: May 25, 2011, 09:18:33 am »
Quote from: dj_dead on May 25, 2011, 08:06:39 am
june 2008 paper 6 q5 part ii


when we get phi(t) = 0.7389
then how come the next step is
phi (t) = phi (0.64)


where did 0.64 come from? =S

I guess the question/question paper you stated isn't the question you are confused about.

Anyway, i dont know the q, but i guess i understand ur doubt.

phi(t) = 0.7389
Meaning, for which value of 't' is the area 0.7389. For this u gotta look at the normal distribution table. You'll find it in the CIE S1 book
and the syl.

I've attached the part of the table where I found 0.7389. If you look closely, you'll see that cell (red) is in the 6th column (starting from column 'z') and the 7th row (starting from 0.0). 0.60 + 0.04 = 0.64,
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Offline melony

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Re: S1 DOUBTS HERE!!!!
« Reply #208 on: May 25, 2011, 05:56:01 pm »
For something like (x>35) how do you know when to use     x.5-meuow/s.d. how do you know its x.5 and not x, is there a pattern!! agghhh!! im panicking before my s1 exam!!  :'( help someone!! like for 62/ON/10 qs 6 (iii) i had no clue which one to use!! :/!!  ??? :(
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Offline SkyPilotage

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Re: S1 DOUBTS HERE!!!!
« Reply #209 on: May 25, 2011, 06:00:36 pm »
Quote from: melony on May 25, 2011, 05:56:01 pm
For something like (x>35) how do you know when to use     x.5-meuow/s.d. how do you know its x.5 and not x, is there a pattern!! agghhh!! im panicking before my s1 exam!!  :'( help someone!! like for 62/ON/10 qs 6 (iii) i had no clue which one to use!! :/!!  ??? :(
Listen: You use the .5 thing (called Continuity correction) When you use Normal Approximation instead of binomiall.....For Example:
If its > then its 35.5
IF its < then its 34.5
If its > or equal its 34.5
If its < or equal its 35.5
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