IfXis a normal random variable with parametersμ= 10 andσ2= 36, compute
a)P(X >5)
b)P(4< X <8)
c)P(X <8).
Given ,
= 10 , = sqrt(36) = 6
we convert this to standard normal as
P( X < x) = P( Z < x - / )
a)
P( X > 5) = P( Z > 5 - 10 / 6)
= P( Z > -0.8333)
= P( Z < 0.8333)
= 0.7977
b)
P( 4 < X < 8) = P( X < 8) - P( X < 4)
= P( Z< 8 - 10 / 6) - P( Z < 4 - 10 / 6)
= P( Z < -0.3333) - P( Z < -1)
= 0.3695 - 0.1587
= 0.2108
c)
P( X < 8) = P (Z < 8 - 10 / 6)
= P (Z < -0.3333)
= 0.3695
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