The diameter of a spherical bob, when measured with vernier callipers yielded the following values : $3.33 \mathrm{~cm}, 3.32 \mathrm{~cm}, 3.34 \mathrm{~cm}, 3.33 \mathrm{~cm}$ and $3.32 \mathrm{~cm}$. The mean diameter to appropriate significant figures is :