Question:
A student measuring the diameter of a pencil of circular cross-section with the help of a vernier scale records the following four readings $5.50 \mathrm{~mm}, 5.55 \mathrm{~mm}, 5.45 \mathrm{~mm}$, $5.65 \mathrm{~mm}$, The average of these four reading is $5.5375 \mathrm{~mm}$ and the standard deviation of the data is $0.07395 \mathrm{~mm}$. The average diameter of the pencil should therefore be recorded as:
Correct Option: , 4
Solution:
(4) Average diameter, $d_{\mathrm{av}}=5.5375 \mathrm{~mm}$
Deviation of data, $\Delta d=0.07395 \mathrm{~mm}$
As the measured data are upto two digits after decimal, therefore answer should be in two digits after decimal.
$\therefore d=(5.54 \pm 0.07) \mathrm{mm}$