finding the me from a group Delta table group page tables can give us a several questions such as mean histograms and cumulative frequency we're going to estimate finding the mean on this chart there are test scores from 0 220 group together so not to seven people scored from not to 10 and 11 people scored from 10 to 30 or way up to three people scoring between 100 and 120 to find the mean I need to add two more columns we're going to take an estimate so we're going to find first of all the midpoint and you can member the word midpoint that starts with the same matter as mean and then we're going to multiply these two together the frequency and the midpoint Sigma mean midpoint and multiply I need to find the midpoint between 0 and 10 which is 5 between 10 and 30 is 20 between 30 and 50 is 40 between 50 and 60 is 55 between 60 and 80 is 70 between 80 and 100 is 90 and 3 one hundred and hundred and 20 is a hundred and ten I now need to multiply the frequency by the midpoint to fill in the fourth column so I multiply 7 by 5 to give me 35 xi multiplied by 20 is 220 14 multiplied by 40 it's five hundred and sixty 16 x 55 is 880 20 x 70 is 1400 9 x 90 is 810 and finally three multiplied by hundred and ten is three hundred and twenty finding estimate of a mean is normally worth about three or four marks so it's definitely worth showing your method as you've gone along because even if I forget what I'm doing now I've scored to one or two marks by filling in these two columns next I need to find the total of the frequency column so I'm going to add all these up together to give me 80 sometimes it will tell you the question it will say 80 people took a test so you've just checked that you've got the same over here and now I need to add together the final column which is a frequency time midpoint column and that gives me a total of four thousand two hundred and thirty five now to find the mean I need to divide the fourth column total by the second column total so that's four thousand two hundred and thirty-five divided by eighty which gives me an answer 52 point nine three seven five I'm going to round this answer and because if digit here is seven is larger than five I'm going to round up and my final answer will be 52 point nine four