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First off, be warned: I am a complete stats novice. I'd like to learn, but at the moment I have an intense business problem to solve that I think (hope?) is straightforward enough that it could be answered easily. I will try to explain as simply as I can so I don't muck it up.

In short, i'm trying to find the right way to display a collection of pie charts. These pie charts are part of a proposal for new business; they measure incumbent capture across multiple contracts from different teaming partners.

Data I'm working with:

  • Company A: [a1] percentage of capture across [b1] contracts
  • Company B: [a2] percentage of capture across [b2] contracts
  • Company C: [a3] percentage of capture across [b3] contracts
  • Total: [aT] percentage of capture across [bT] contracts

I have the data for sets 1, 2, and 3 -- the goal is to derive the data for set "T".

Essentially, we'd like to say "business A had 30% capture across 100 contracts, business B had 50% against 70 contracts, and business C had 40% against 500 contracts" the individual pie charts are of course simple enough (even I can do that one ;) ), but I would like them all to feed into a pie chart which shows the average percentage across all contracts with the total of contracts.

To try to articulate more bluntly, my question is: how can I ensure that the individual percentages for company performance are weighted according to the number of contracts they are referencing?

Thank you in advance for any help you can give!

All the best,

--Sean

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  • $\begingroup$ This question was tagged with "pie-chart" but it seems to involve some kind of intermediate computation, and your own response didn't address the data visualization issue. Could you update it accordingly? $\endgroup$
    – chl
    Commented Apr 3, 2011 at 10:48

1 Answer 1

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It might be easier than I thought -- please let me know if this is correct or on the right path.

Let's assume the following data:

  • Company A: 70 percentage of capture across 10 contracts
  • Company B: 60 percentage of capture across 100 contracts
  • Company C: 50 percentage of capture across 40 contracts

First, I figured out the percentage of each contractors contribution to the total amount of contracts, so:

  • Company A: 6.67% of total contracts
  • Company B: 66.67% of total contracts
  • Company C: 26.67% of total contracts

I then took the company's capture rate and multiplied it by their percentage of total contracts, so:

  • Company A: 4.67% contributing to total percentage
  • Company B: 40% contributing to total percentage
  • Company C: 13.33% of contributing to total percentage

Which makes the total:

  • 58.00% across 150 contracts

Please let me know if this is correct (or close enough). Thanks!

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    $\begingroup$ good answer, it could be improved by writing out the steps to get each number, e.g. $6.67\text{%}=\frac{10}{10+100+40}\times 100\text{%}$. similarly for second step $4.67\text{%}=6.67\text{%}\times 70\text{%}$. If you have the equations as well as the words, people are less likely to get confused $\endgroup$
    – probabilityislogic
    Commented Apr 3, 2011 at 3:38
  • $\begingroup$ Here are a couple things that may make you trust that you've done it properly. These may also make better information displays: (1) Scale the pie charts according to the number of contracts per company pie; (2) Draw stacked bar charts (same as pie charts but in a line instead as a circle), cut them out and arrange the capture and non-capture cut-outs in two bars. $\endgroup$
    – Avery Richardson
    Commented Apr 3, 2011 at 15:04
  • $\begingroup$ Thank you both for the comments! @probabilityislogic, you're absolutely right from a technical perspective. This is being done for a business proposal though, and so unfortunately we need to conserve space. I was mostly looking for a way to ensure our visualizations would be mathematically correct. @Thomaas, I do have plans to scale the pie charts, I just wanted to make sure the numbers were technically correct. $\endgroup$
    – SeanKilleen
    Commented Apr 8, 2011 at 20:51

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