Question

The measurements of a source voltage are 5.9 V, 5.7 V and 6.1 V. The sample standard deviation of the reading is

• A. 0.013
• B. 0.04
• C. 0.115
• D. 0.2

Answer 1

The correct option is D 0.2

Arithmetic mean

$\overline{x}=\frac{5.9+5.7+6.1}{3}=\frac{17.7}{3}=5.9$

$Deviation{d}_1={\overline{x}}_1-\overline{x}$

= 5.9 - 5.9 = 0

$Deviation{d}_2={\overline{x}}_2-\overline{x}=5.7-5.9=-0.2$

$Deviation{d}_3={\overline{x}}_3-\overline{x}=6.1-5.9=0.2$

Standard deviation

$\sigma =\sqrt{\frac{\sum d^2}{n-1}}(asn<20)$

$\sigma =\sqrt{\frac{(0{)}^2+(-0.2{)}^2+(0.2{)}^2}{(3-1)}}=0.2$