Answer:
a) P(X < 24) = 0.1151
b) P(24 < X < 36) = 0.7698
c) X value for P(x < X) = 0.95 is X = 38.225
Step-by-step explanation:
a) P(X < 24)
Since μ = 30 and σ = 5 we have:
[tex]\text {z value = } \dfrac{24-30}{5}} = -1.2[/tex]
P(X < 24) = P(Z < -1.2) = 0.1151
You can use a calculator or the standard normal tables to determine P(Z < -1.2)
b) P(24 < X < 36)
First find P(X < 36) using the technique detailed in part a)
For 36, the Z value is
[tex]\dfrac{36-30}{5} = 1.2[/tex]
P(X < 36) = P(z < 1.2) = 0.8849
P(24 < X < 36) = P(X < 36) - P(X < 24) = 0.8849 - 0.1151 = 0.7698
c) X value below which 95% of the area is covered
Using a calculator (or tables) the z value corresponding to P(z < Z) = 0.95 is Z = 1.65(approx)
[tex]\text{We have } \dfrac{X - \mu}{\sigma} = z\\\\\dfrac{X - 30}{5} = 1.645\\\\\text{Multiplying both sides by 5: }\\\\X - 30 = 1.645 \times 5 = 8.225\\\\X = 30 + 8.225 = 38.225[/tex]
So X value is 38.225-