Question

If the probability of a defective bolt is $0.1$. The mean and standard deviation for the distribution of defective bolts in a total of $400$.... & ....

• A. $40,36$
• B. $40,6$
• C. $20,6$
• D. $10,6$

Answer 1

Answer: (B)

$40,6$

Mean will
$np$
$=n\left(0.1\right)$
$=400\left(0.1\right)$
$=40$
And variance will be
$np(1-p)$
$=40(1-0.1)$
$=40\left(0.9\right)$
$=36$
Therefore the standard deviation is $\sqrt{36}$
$=6$