Give more details by showing average and distribution [Charting Tips]

Posted on April 6th, 2011 in Charts and Graphs - 7 comments

When we have lots of data, we try to summarize it by calculating the average. As they say, averages are mean, they do not give away much.

I want to share with you an interesting example from Amazon.com on how they give more details by combining average with distribution.

As you might know, Amazon shows the rating of each of the products they sell. Customers & users rate the products from 1 to 5 stars. When you visit the product page you will see the average rating. But there is a small down-arrow next to it. When you click on it, Amazon shows you the break-up of that rating so you have a better idea of how the ratings are split.

Give more details by showing average and distribution

Why show distributions?

Showing distribution of values corresponding to the average reveals important information about the data. We tend to use averages alone since they take very little time to compute and very little space to show. But adding the ability to show distribution of values (on demand) is a powerful way to let end-users understand the data better. [related: calculating frequency distributions in excel]

Below, I have shown a demo of how you can do this using Excel. Tomorrow, I will write a tutorial explaining the same.

On-demand Details in Excel Charts – a Demo:

Showing distribution of values on-demand is a good way to help readers understand the data better

What is your Opinion – Averages / Distributions / Both or Something else?

I prefer to use simple metrics like average, median, sum, count, min or max at the high-level in my dashboards or charts. But I always add extra detail by showing distribution of values or break-up by a different parameter so that my audience can understand the outputs better.

What about you? What metrics do you use at high-level and how do you add detail? Please share your thoughts and techniques using comments.

More Charting Principles:

There are tons of very good charting examples around us. Once in a while, I write about these on chandoo.org. I recommend reading the below articles if you make charts,

Written by Chandoo
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7 Responses to “Give more details by showing average and distribution [Charting Tips]”

  1. Cyril Z. says:

    Hi Channdo,

    I really want to know more about this one. I hHardly can till tomorrow 🙂

    But I'd have put the details from 5stars to 1 star, since usually top is better.

    Cyril

  2. Juan Velez says:

    Chandoo:
    This is great! I am struggling with displaying average and distribution on a single page as we speak. I am submitting my report by the end of the week and this technique looks like it will save me! Thanks again for your great blog and community you have built aroun it. Glad I found it.

    Thanks, JV

  3. Kelly says:

    Chandoo,

    An average does not show how the results are dispersed, as a result, an entire dimension of information is omitted. Dispersion of results cna indicate how likely you may be to having the same result as other reviewers, and can help in showing potential predictablility. It would be the same as quoting a rate of return for an investment without sharing how volatile that investment has been. The average of (1) one star rating and (1) five star rating would be three stars ad that may be acceptable, but this may show you have as much chance buying a product that turns out to be unusable as it does great.

    Be well,

    Kelly

  4. Fred says:

    I'm interested in how the raw data was tabulated in the first place. that'll determine how info is displace from the data table. 😉

  5. Christian says:

    Chandoo,

    Like you, I'm a fan of the KISS approach.

    Use simple calculations - display things simply etc. I find you increase the value of your work by keeping it simple, clean and unambiguous. (as a general rule).

    But would suggest a point of comparison - in many instances data can be meaningless without a benchmark.

    e.g: a score of 4 out of 5 might sound good, but if every other movie is scoring 5 out of 5 it suddenly doesn't look as impressive.

    So perhaps integrating an option where you can view the distribution of one particular movie (as above), in relation to the average distributions, or the number one achievement etc.

    Many Thanks

    Christian

  6. [...] we have seen a beautiful example of how showing details (like distribution) on-demand can increase the effectiveness of your [...]

  7. Striker says:

    This is something i wanted to know how to do some time back. I could not find much info about it online and always wondered how to do it.

    Then, in the end i settled with just the usual meter ranging from 1-100% using value and goal as shown.

    Now that i know how to add images and masking...i will be wiling to try it out again.

    Thank you Chandoo for posting this info!

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