Question

The mean diameter of a thin brass rod is to be measured by vernier callipers. Why is a set of 100 measurements of the diameter expected to yield a more reliable estimate than a set of 5 measurements only?

Answer 1

• Due to random errors, a large number of observations (say, 100) will give a more reliable result than a smaller number of observations (say, 5).
• This is due to the fact that the probability (chance) of making a positive random error of a given magnitude is equal to that of making a negative random error of the same magnitude.
• Thus, in a large number of observations, positive and negative errors are likely to cancel each other. Hence, a more reliable result can be obtained.