question about finding medians

why do you sometimes add 1 to the sum of the frequency then divide by 2, but other times you just divide the sum of the frequency by 2 to find the median. im just confused

Reply 1

stressingrn

this is about maths statistics 1 btw

Reply 2

ghostwalker

Original post by Maryyyxxx

why do you sometimes add 1 to the sum of the frequency then divide by 2, but other times you just divide the sum of the frequency by 2 to find the median. im just confused

If you're working with ungrouped data then you should be using (n+1)/2; and this will give you the midpoint every time.

If you're working with grouped data, then it's n/2; the argument being, according to my stats. book, is that if you used (n+1)/2 then working up the values would give you a different point to working down the values when looking at a cumulative frequency polygon/curve.