Question

If a student measured the mass of an object on a balance three times and obtained the values 14.568 g, 14.566 g, and 14.565 g, the range and percent of the average value between the measurements would be ____________

(a) 0.005gm, 0.01%

(b) 0.004gm,0.02%

(c) 0.003gm,0.02%

(d) 0.001gm,0.01%

The question was asked during an interview.

My question is taken from Errors in Data and Calculations topic in section Presentation and Analysis of Data of Bioprocess Engineering

Answer 1

The correct option is (c) 0.003gm,0.02%

Explanation: Range = (14.568 – 14.565) g = 0.003 g,

This is a reasonable range; the uncertainty appears in the last significant figure of the measured value, as it should.

The average value for the mass of the object is 14.566 g. Therefore:

% of average = (0.003 g/14.566 g) x 100% = 0.02%

the range as a percent of average (RPA) has only one significant figure in this case because the numerator of the fraction has only one.