Question

The standard deviation of a normallydistributed data set is 9. If 100 is 3 standarddeviations above the average value of the set,what is the value of the mean?(I really need help with this..)

Answer 1

Apply the formula:

$z=\frac{x-\upsilon}{\sigma}$

Where:

z= 3

x = value = 100

μ = mean = ?

σ= standard deviation = 9

Replacing:

$3=\frac{100-\mu}{9}$

Solve for the mean

3 *9 = 100- u

27 = 100-u

u = 100-27

u= 73

mean = 73