In: Statistics and Probability
X1, X2, ... , X34 is a random sample from a distribution with mean μ = 7.26 and variance σ2 = 13.10
1) Find P(X ≤6.13)
2) Find P(X >6.13)
3) Find P(6.85 < X≤ 7.85)
Solution :
Given that ,
= 7.26
2 = 13.10
= 2 = 13.10 = 3.62
= / n = / 34 = 0.62
a) P( 6.13 ) = P(( - ) / (6.13 - 7.26) / 0.62)
= P(z -1.82)
Using z table
= 0.0344
b) P( > 6.13) = 1 - P( < 6.13 )
= 1 - P[( - ) / < (6.13 - 7.26) / 0.62]
= 1 - P(z < -1.82 )
= 1 - 0.0344
= 0.9656
c) P(6.85 < 7.85)
= P[(6.85 - 7.26) / 0.62 < ( - ) / (7.85 - 7.26) / 0.62)]
= P(-0.66 < Z 0.95)
= P(Z 0.95) - P(Z < -0.66 )
Using z table,
= 0.8289 - 0.2546
= 0.5743