What is median by interpolation and how can it help me find the median?

[MightyMeanie]

I was doing some last minute skimming through my book for my exam tomorrow and panic. Can someone please please tell me about finding the median by interpolation and perhaps an example of how it would could used or asked, i will be forever greatful

yasmin x
(i can only find a small paragraph in my book which doesn't tell me much )

 

[MightyMeanie]

is it:

Q2 = ((n/2 * f)/fc) * c

b - lower class boundary
f - sum of all frequencies below b
fc - frequency of the class width containing quartile required
c - class width of required class
n - total frequency