# Linear Change of Variance - S1?Watch

#1
Hello,

I'm revising for my S1 edexcel AS exam, and looking through the specification saw that 'linear change of variance may be required.' This was under the correlation and regression section.

I have never done it, so if anyone could explain it in the context of the unit(correlation and regression) that would be great thanks!

Thanks everyone
0
7 years ago
#2
In general, if is a random variable and is any number, then . Also, if are independent, then . [So combining these we get .]

I'm not sure how much of this is relevant to the S1 syllabus, but provided you know what correlation is and so on, you can work out how this will affect your results. If you're still clueless or if this isn't what you're getting at, then see what your textbook has to say -- if there's nothing there, then you either probably won't need it, or you already know the result without knowing you know it.
7 years ago
#3
Suppose you have 2 variables x and y with correlation coefficient r, then if you apply a linear coding to either x or y, i.e
X= ax +b and Y=cy +d where a,b,c,d are constants then the correlation coeff of X and Y is also r.

For variance there's the result Var(ax + b) = (a^2)Var(x) for any constants a and b.
0
#4
Thanks!

I still don't really get it, but it's not in my textbook so I'll assume we don't need to know it!
0
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