Question

The standard deviation of linear dimensions P and Q are $3\mu m\text{and}4\mu m$ respectively. When assembled, the standard deviation $\left(in\mu m\right)$ of the resulting linear dimension (P + Q) is .

• A. 5

Answer 1

The correct option is A 5

${\sigma }_P=3\mu m$
${\sigma }_Q=4\mu m$
${\sigma }_P^2=9$
${\sigma }_Q^2=16$
${\sigma }_{(P+Q)}^2=9+16=25$
${\sigma }_{(P+Q)}=5$

[Variance can be added]