University of the West of England



Propagation of Uncertainty (Calculation of resistivity)


Link to Video Answer


The electrical resistivity, ρ (Ω m), of a material can be found from the following equation:


by measuring the resistance R (Ω) of a wire of cross sectional area A (m2) and length L (m).

The resistance, area and length of a piece of wire are measured with the values given in the table




Standard deviation


Resistance, R

1.50 Ω

0.02 Ω

Cross sectional area of wire, A

7.910-9 m2

0.210-9 m2

Length of wire. L

0.300 m

0.002 m


Use Excel to calculate the

i)          value of the resistivity, ρ,

ii)         standard deviation uncertainty in ρ, and

iii)         95% confidence interval in ρ.