Median formula for grouped data?

Simple answer:
Divide the total number of observations (plus 1, if small) by 2 to find the middle rank.

Look at the cumulative frequencies for the grouped data and find the group in which the middle rank would appear. That is the median group.

More sophisticated answer:
Withing the median group, interpolate.
Simple answer:
Divide the total number of observations (plus 1, if small) by 2 to find the middle rank.

Look at the cumulative frequencies for the grouped data and find the group in which the middle rank would appear. That is the median group.

More sophisticated answer:
Withing the median group, interpolate.