Let us prepare the frequency distribution table.
= 67.5 – 6.85
= 60.65
and Standard deviation,
\(σ=\sqrt {h^2[\frac{1}{N}\displaystyle\sum f_iu_i^2-(\frac{1}{N}\displaystyle\sum f_iu_i)^2}]\)
\(= \sqrt{255[ \frac{733}{230}-(-\frac{105}{230})^2]}\)
\(= \sqrt{255[3.187-(0.46)^2]}\)
\(= \sqrt{669.465}\)
= 25.87
∴ Mean = 60.65,
Standard deviation = 25.87
