Hi Nadya,
I am using rather old book but related to real life "Basic Statistical Concepts" by Jack I. Bradley. It has not formula for median (as maths formula) however I understand that forumulas presented by Bruce reflect the idea of using median. I think that below quote would be interesting:
"A second measure of central tendency is median. The median is the value above which half of the measure lie. It is used when the distribution is badly skewed - when the measures are piled up at one end of the distribution rather than being more or less simmetrically distributed about the mean... When a distribution is skewed, the median is a better indicator of the central point about which most of the scores cluster...
There is a formula for finding the exact value of median in cases when it is not as obvious as in the example. However, it is often sufficiently accurate just to rank the measures from high to low and count down to the middle of the distribution."
I feel that with my sets of data this precision is sufficient (even with sometimes limited number of scores) - the median is an indicator for me not a factor in i.e. accounting calculations. In fact knowing quality of the most statistical data going much further with precision would be an "academic" exercise.
Bedst regards
Jacek