For grouped data

Mean:

The mean of a sample of data organized in a frequency distribution is computed by the following formula:

X is considered as the mid point of the range.

Median:

The median of a sample of data organized in a frequency distribution is computed by the
following formula:

Median = L + [(n/2 - CF)/f] (i)

• L is the lower limit of the median class
• CF is the cumulative frequency preceding the median class
• f is the frequency of the median class
• i is the median class interval.

Mode:

The mode for grouped data is approximated by the  midpoint of the class with the largest class frequency.