Question

The students are given a vernier calipers to measure the outer diameter of a cylinder. The actual outer diameter is 4 cm. The measurements made are given in the following table:
$\begin{array}{cccccc}Student& Measurements& & & & \\ & 1& 2& 3& 4& 5\\ A& 4& 4& 4& 4& 4\\ B& 3.5& 3.6& 3.7& 3.8& 3.65\\ C& 3.7& 3.9& 4.1& 4.3& 4\\ D& 3.6& 4.2& 4.4& 4.8& 4.25\\ E& 4.005& 3.995& 4.05& 3.95& 4\end{array}$

1. In case A, the measurements are said to be:

• A. Accurate
• B. Precise
• C. Both a & b
• D. none

Answer 1

The correct option is C

Both a & b

Go back to the arrow analogy from the archer story. When the archer hit his target apple in his practice shots repeatedly we said that he was both accurate and precise.
Similarly, in this case we say that the measurements made by the students are both accurate and precise.

Note: This is an idealistic case where we get the actual measurement of something which is not possible in reality. In realistic measurements we always have some degree of error associated with measurements so we can never say that any measurement is absolutely accurate or precise, but we can only talk about the degree to which it is accurate or precise. So when we talk about relative accuracy and precision, terms like high accuracy and low accuracy come into picture.