Question

7)

The test scores are normally distributed with a mean of 50 and a standart deviation of 5. If P (X > X₁) = 0.8438.

X₁ = ?

Answer 1

Given that,

mean = = 50

standard deviation = =5

Using standard normal table,

P(Z > z) = 0.8438.

= 1 - P(Z < z) = 0.8438.

= P(Z < z ) = 1 - 0.8438.

= P(Z < z ) = 0.1562

z = -1.01 (using standard normal (Z) table )

Using z-score formula  

x = z * +

x= -1.01* 5+50

x= 44.95

X1 = 44.95