平均值:x=(802.40+802.50+802.38+802.48+802.42+802.46+802.45+802.43)/8 =802.44m

單次測量方差V1=(802.44-802.40)*(802.44-802.40)=16

V2=(802.44-802.50)*(802.44-802.50)=36

V3=(802.44-802.38)*(802.44-802.38)=36

V4=(802.44-802.48)*(802.44-802.48)=16

V5=(802.44-802.42)*(802.44-802.42)=4

V6=(802.44-802.46)*(802.44-802.46)=4

V7=(802.44-802.45)*(802.44-802.45)=1

V8=(802.44-802.43)*(802.44-802.43)=1

[vv]=16+36+36+16+4+4+1+1=114

標準差(中誤差):m=±√[vv]/n-1

=±√114/7

=±4.04mm

極限誤差:Δ=3m=3*4.04=12.12mm

算術平均值的標準差:M= ±m/√n

= ±4.04/2.83

= ± 1.43mm