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Given Data :

Normal Distribution function

$$P(x \leq -1) = P(y \geq 2)$$

x : mean= 1 variance= 4

y : mean= -1 variance= to be found..?.

Ans: 9

How to solve..?

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1 Answer 1

up vote 1 down vote accepted

Firstly, $P(x\le-1)=\Phi\left(\frac{-1-1}{\sqrt4}\right)=\Phi(-1)$ Also, $P(y\ge2)=P(y\le-4)=\Phi\left(\frac{-4-(-1)}{\sigma}\right)=\Phi\left(\frac{-3}{\sigma}\right)$.

So we have $\frac{-3}{\sigma}=-1$ and $\sigma^2=9$.

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Thank you............:) –  Jay Satish Teli Feb 9 '13 at 11:55

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