# Compound bar chart - to round or not round percentages?

1. Dec 14, 2013

### 3vo

1. The problem statement, all variables and given/known data
Hi,
My task is to draw a compound bar chart. As I understand, with this type of bar chart; each group of data is represented by a single bar which is equivalent to 100%. The sub data within that group is divided into a percentage of the total 100% and drawn into the grouping bar, splitting the bar into percentage counterparts of the whole bar.

The problem is for some of my data which initially are integers but when calculating percentages become fractions/decimals (some repeating). I dont know how to use this data when incorperating into my graph. Do I round up or down? or try to best draw them into my graph.

Normally I would round my answer to the same number of dp or sf as the lowest value in the question. However in this case, my initial numbers are integers, so if I round up or down to the same number of SF or DP, the total sum of my percentages do not add up to 100%.

In this case, (similiar to if I were doing a pie chart) do I round to the nearest whole number and than add or subtract whatever remains from the largest percentage value as it would make the least diff?

2. Relevant equations
Imagine a table below:

Mon Tues Wed
Red 7 (30.'43%) 3 (18.75%) 2 (20%)
Blue 10 (43.'47%) 7 (43.75%) 6 (37.5%)
Black 6 (26.'08%) 6 (37.5%) 5 (50%)
Total 23 (100%) 16 10

3. The attempt at a solution

Round the numbers to 2 sf and add or subtract the extra from the largest percentage.
So for monday
Red: 30
Blue: 43
Black: 26
total: 99

Add remaining 1% to blue (43+1=44) to now have a total of 100% as it makes the least difference adding to largest percentage.

Would this be the correct method?

Last edited: Dec 14, 2013
2. Dec 14, 2013

### Staff: Mentor

Draw them as accurate as possible (a computer will do that anyway, by hand see how accurate you can draw it, I guess .5% are not visible), and display the percentages rounded to integers. The sum is 100%, even if 30+43+26=99, that is okay.