Given data
1. The mean
[tex]\frac{\sum fx}{\sum f}=\frac{505}{66}=7.6515[/tex]
2. The median
[tex]\begin{gathered} \text{ Median = (}\frac{\text{N+1}}{2})th \\ =(\frac{66+1}{2})th=(\frac{67}{2})th=33.5th \\ \text{The median is the 33.5th }term\text{ which is between 7 and 8} \\ \text{The median is }\frac{\text{7+8}}{2}=\frac{15}{2}=7.5 \end{gathered}[/tex]
3. The sample standard deviation
[tex]\begin{gathered} SD\text{ =}\sqrt[]{\frac{\sum f|x-\bar{x}|}{\sum f}} \\ \bar{x}=7.6515 \\ SD=\sqrt[]{4.8028} \\ SD=2.1915 \end{gathered}[/tex]