b
\(T\,\, = \,\,\frac{{2.63\,\, + \;\,2.56\,\, + \;\,2.42\, + \;\,2.71\,\, + \;2.80}}{5}\)

\( = \,\,\frac{{13.12}}{5}\,\, = \,\,2.624\,\, \cong \,\,2.62\)

\(\begin{gathered}
  \left( 1 \right)\,\,2.62\,\, - \,\,2.63\,\, = \, - 0.01 \hfill \\
  \left( 2 \right)\,\,2.62\,\, - \,\,2.56\,\, = \,\, + 0.06 \hfill \\
  \left( 3 \right)\,\,2.62\,\, - \,\,2.42\,\, = \,\, + \;\,0.20 \hfill \\
  \left( 4 \right)\,\,2.62\,\, - \,\,2.71\,\, = \,\, - 0.09 \hfill \\
  \left( 5 \right)\,\,2.62\,\, - \,\,2.80\,\, = \,\, - 0.18 \hfill \\ 
\end{gathered} \)

સરેરાશ નિરપેક્ષ ત્રુટિ \( = \frac{{0.01\,\, + \;\,0.06\,\, + \;\,0.20\,\, + \;\,0.09\,\, + \;\,0.18}}{5}\,\)

\( = \frac{{0.54}}{5}\,\, = \,\,0.108\,\, \cong \,\,0.11s\)