Question

Standard normal probability distribution has mean equal to $40$, whereas value of random variable x is $80$ and z-statistic is equal to $1.8$ then standard deviation of standard normal probability distribution is

• A. $150$
• B. $80$
• C. $40$
• D. $11.11$

Answer 1

The correct option is D $11.11$

Given Mean $\overline{x}=40$ $x=20$ $z=-1.8$

$\Rightarrow z=\frac{x-\overline{x}}{\sigma }$ $\to \sigma =\frac{x-\overline{x}}{z}$

$\Rightarrow \sigma =\frac{20-40}{-1.8}=11.11$

Hence, the answer is $\mathrm{11.11.}$