I have a set of data in exclusive form. The Time(class limit) is from 0-20, 20-40, 40-60, 60-80 and 80-100. The frequency in bracket of each classes are as follow 0-20(f=2), 20-40(f=15), 40-60(f=20), 60-80(F=10), 80-100(f=3).
I was asked to find the mean and median and standard deviation of this data. The mean was 48.8. I divide the total sum of (frequency × midpoint) 2440 by total frequency sum which is 50. Now for the median. I am not sure how to calculate my class boundaries. Can class boundaries here be zero? if so will my first class boundary be -0.5 - 19.5? and my second class boundary 19.5 - 39.5?