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 mm, 5.55 mm, 5.45 mm, 5.65 mm. The average of
these four readings is 5.5375 mm and the standard deviation of the data is 0.07395 mm. The
average diameter of the pencil should therefore be recorded as :