I am making a survey that assesses people’s concerns about a particular situation. At the end of this process, I want to create a pie chart that establishes how much each stated concern factors into the overall situation. But here is my problem: the survey asks each person to list 1-6 concerns, but they don’t need to use all 6-- just as many as they see fit. Then they list a percentage next to each item they list such that if you add up all the percentages they write down, you will get 100%.

How would I mathematically calculate what percentage each factor stated figures into the overall scheme of concerns? This would be easy if everyone had an equal number of concerns, but they don’t. Any help?

Just add up the percentage for each concern and divide by the total number of respondents (in other words: calculate an average).

Thus, if two people have 30% and 50% for concern 1, the average amount of concern is 40% and that’s what will take up 40% of the pie chart. If they score concern 2 at 30% and 0%, then average amount of concern is 15%.

Since 100% has to be allocated, your final averages will always add up to 100% and give you a nice pie chart.