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S1 and S2 DOUBTS HERE!!!!

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dj_dead:
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

EMO123:

--- 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

--- End quote ---
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

Ghost Of Highbury:

--- 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

--- End quote ---

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,

melony:
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!! :/!!  ??? :(

SkyPilotage:

--- 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!! :/!!  ??? :(

--- End quote ---
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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