Suppose X is a normally distributed random variable with mean μ = 10 and variance σ2 = 4. Find P(9 < X < 12).
Solution :
Given that ,
mean = = 10
standard deviation = = 4=2
P(9< x <12 ) = P[(9-10) / 2< (x - ) / < (12-10) /2 )]
= P( -0.5< Z < 1)
= P(Z <1 ) - P(Z < -0.5)
Using z table
= 0.8413-0.3085
probability= 0.5328
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