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S1 and S2 DOUBTS HERE!!!!

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astarmathsandphysics:
Find
E( x^2 + 4X - 3)
E(x) = 2.6
and the answer = 15.6
how did they get it ??
You must know the variance to answer this question. What is it?

coatseville:
I have two questions...
From the January 2009 paper
question 3e) could you please explain fully how to do this..
and for 2b) why must we use the addition rule? When we didnt in 2a)
Thankyou SO much :)

Summer :]:

--- Quote from: astarmathsandphysics on May 26, 2010, 02:59:23 pm ---Find
E( x^2 + 4X - 3)
E(x) = 2.6
and the answer = 15.6
how did they get it ??
You must know the variance to answer this question. What is it?

--- End quote ---

Var 1.44

astarmathsandphysics:
Find
E( x^2 + 4X - 3)
E(x) = 2.6
and the answer = 15.6
how did they get it ??
You must know the variance to answer this question. What is it?

Var 1.44
V(X0=E(X^2)-(E(X))^2
1.44=E(X^2)-2.6^2
E(X^2)=1.44+6.76=8.18
E( x^2 + 4X - 3)=E(X^2)-4E(X)-3=8.18-4*2.6-3=8.18-1.4=-5.22

Blizz_rb93:
June 2001
Question 1 a)
they said to find the mean and the standard deviation for the data given
in the markscheme they gave something different to what i solved
the mean i knew how to do but the standard deviation was the weird part

My solution : Standard Deviation = Square root of [(sum of x^2 divided by n)-(mean)^2]
my answer gives me Math Error

and in the markscheme the answer comes out 4 :/
plz someone help asap
thank you

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