Question

X is a normally Distributed random variable with a standard deviation of 4.00. Find the mean of X when 64.8% of the area lies to the left of 8.52.

Answer 1

Answer:

7

Step-by-step explanation:

σ = 4 ; μ =?

8.52 to the left of X

.

P(X < 8.52) = 64.8%

P(X < 8.52) = 0.648

Using the Z relation :

(x - μ) / σ

P(Z < (8.52 - μ) / 4)) = 0.648

The Z value of 0.648 of the lower tail is equal to 0.38 (Z probability calculator)

Z = 8.52 - μ / 4

0.38 = 8.52 - μ / 4

0.38 * 4 = 8.52 - μ

1.52 = 8.52 - μ

μ = 8.52 - 1.52

μ = 7