Question

mean of 15 standard devistion of 3. looking for the variables between 50%

Answer 1

Solution

Given that,

P( -z < Z < z ) = 0.50

P( Z < z ) - P( Z < -z ) = 0.50

2*P(Z < z ) - 1 = 0.50

2*P(Z < z ) = 1 + 0.50

P( Z < z ) = 1.50 / 2

P( Z < z ) = 0.75

P( Z < 0.674) = 0.75

z = 0.674

and

z = -0.674

Using z - score formula,

X = z * +

= 0.674 * 3 + 15

= 17.022

X = z * +

= -0.674 * 3 + 15

= 12.978

The variables between 50% is 12.978 and 17.022