Monday, 28 July 2014

How to Use a Bubble Chart

We frequently wonder about reporting users creating huge analyses based on table views in their BI application. When asking for the intention we get two oppositional replies:
  1. We need all this data to get the information needed.
  2. The business question is a detailed one and they just seek for one specific information.
From our point of view both statements have the same origin. BI users just don't know how to visualise the business request, because it's a wide field of interest. And tables are well known from Office applications. Reporting and analysis requirements are mainly split into two areas:
  1. How to gather and calculate the required information on available data?
  2. How to visualise the information to recognise context fast and easy?
Implementing BI applications and building analysis covers the first area. For the second one we decided to start a series to show you how you can visualise business information to be able to interpret these data without the need of digging around in raw table data. Have a short look to the following table:


Question: "Is there a correlation on sales volume between number of customers and products assigned to a salesperson? If yes, which situation is the best one for increased turnover?"
It's not possible to find the correct answers within seconds when just regarding the table. But when visualising the demand with a bubble chart you get a quick win:

OBIEE Bubble Chart

Horizontal axis shows number of products and vertical axis indicates number of customers. Green indicates a high turnover for a salesperson (represented by a bubble), blue a normal and red a low one. The answers are:
  1. Yes, there is a correlation!
  2. Increasing the number of customers assigned to a salesperson seems to have a positive effect on turnover, but they shouldn't have to sell too much or too less products.
Why? If there would be no correlation you could find green bubbles spreaded in each quadrant. On the top you can only see green bubbles. Therefore a increased number of customers is good for sales volume. Of course, to get a verified picture you'll have to analyse the situation not only once, but that's the indicator.

Summary
When finding an accumulation of equally coloured bubbles in a bubble chart, then you possibly found a relationship between the other figures applied.

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