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S2 help please

hey...the june 2003 paper has a really funny question and i cant find the markscheme anywhere. any help much appreciated!

3. In a town, 30% of residents listen to the local radio station. Four residents are chosen at random
a) state teh distribution (I said Binomial, with n=4 and p=0.3)
b) on graph paper, draw the probability distribution of x
how do i do this?! never seen anything like it before

thanks x
Reply 1
Avatar for zxcvbnm
zxcvbnm
basically draw the graph of probabilitiy (y-axis) against no. of resident
its a silly stupid question and is pointless :eek:
Reply 2
Avatar for jazzyj
jazzyj
OP
as in 0.3 on y axis and 4 on x axis and the two points joined so the graph is like a triangle?
Reply 3
Avatar for zxcvbnm
zxcvbnm
no no... u do the following
X=no.of residnents listening to radio X-B(4,0.3)
calculate the probabilities 0f
P(X=0) , P(X=1) , P(X=2), P(X=3) and P(X=4)
now plot these porbabilites againt 1 ,2 , 3 ,4 respectivley but join points
does that make sense?
Reply 4
Avatar for zxcvbnm
zxcvbnm
sorry i mean dont join the points
Reply 5
Avatar for jazzyj
jazzyj
OP
oo yes it does...so y axis has things like the tables e.g. 0.0237 (random example) and x axis has 0,1,2,3,4

that right?

and kind of like a scatter diagram as in no line joining them all up?
Reply 6
Avatar for zxcvbnm
zxcvbnm
yes u are nearly there

but one thing to note that that i said dont join points BUT do joint numbers (1,2,3,4) with thier probabilities
Reply 7
Avatar for jazzyj
jazzyj
OP
oo ok so u get lots of diagonal lines?

thanks for this! x
Reply 8
Avatar for zxcvbnm
zxcvbnm
u should get straight lines
Reply 9
Avatar for jazzyj
jazzyj
OP
as in diagonal from x axis to y axis i.e. 1 on x joined with prob of 1 on y
Reply 10
Avatar for Adil Bhai
Adil Bhai
horizontal lines goin from x axis directly up to the corresponding probablility

Can u tell me iff we'll get extra binomial tables since in s2 book there is only distribution available for n=5,10,20. So r we gonna get a booklet with probability distributions with variety of values for n?????
Reply 11
Avatar for jazzyj
jazzyj
OP
right thank u!

off to bed now
xx
Reply 12
Avatar for zxcvbnm
zxcvbnm
yes in the formula book u have n= 5,6,7,8,10,12,15,20,25,30......50 something like that

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