Visualising Uncertainty Dr Alasdair Rutherford University of Stirling Firstly we need to think about what we mean by big data. It’s a popular term, widely used in the media, but it can mean different things to different people. There’s no one agreed-upon definition, so I’m going to talk about some of the characteristics of big data and what they mean.

What do we mean by uncertainty?

The simplest way to show uncertainty is the distribution of a variable But showing all the data doesn’t really summarise

Example: Box Plot A box plot shows a number of summary statistics about spread that can help to understand uncertainty

Use measures of spread as well as middle Measures of the middle – mean, median, mode Measures of spread – range, interquartile range, standard deviation Uncertainty in estimates – standard error and confidence intervals

How do we communicate uncertainty in the form of probabilities?

Natural frequencies appear to be superior to percentages in improving understanding of screening tests This is due to the cognitive effort required for interpreting conditional probabilities

How do we communicate uncertainty in predictions?

Areas show probability of different outcomes Compare two scenarios Compare two scenarios Areas show probability of different outcomes

Different uncertainty on different days Show range of predicted temperatures, as well as the average

Confidence intervals around estimates show range of likely values

Show both the prediction and the range of likely possibilities

Fan-chart of possible values shows uncertainty of predictions – and how this changes over time Bank of England refuses to provide point estimate for far-off predictions so that the focus is on the uncertainty

What is the best way to visualise uncertainty? Probabilities are not intuitive – communicate with care! Use multiple formats; different presentations suit different audiences Communicate both absolute and relative probabilities / risks

What is the best way to visualise uncertainty? Well-presented graphics with clear explanations work best Use narratives, images and metaphors that gain attention; but resist arousing undue emotion All visualisations have limitations, showing only part of the story – make it clear what you are and are not showing

Visualising Uncertainty Communicating uncertainty is important, whether you are reporting a simple average or the estimates from statistical modelling Visualisation can be a good way to communicate these uncertainties – and there are a wide range of techniques being developed that can help

Visualising Uncertainty Dr Alasdair Rutherford University of Stirling Firstly we need to think about what we mean by big data. It’s a popular term, widely used in the media, but it can mean different things to different people. There’s no one agreed-upon definition, so I’m going to talk about some of the characteristics of big data and what they mean.