### Introduction

In a previous post I discussed how to plot **confidence intervals** on observed probabilities. Using this method we can create graphs like the following. (Data is in the Excel spreadsheet we used previously: for this post I have added a second worksheet.)

The graph depicts both the observed probability of a particular form *and the certainty that this observation is accurate*. The ‘I’-shaped error bars depict the estimated range of the true value of the observation at a 95% confidence level (see Wallis 2013 for more details).

A note of caution: these probabilities are semasiological proportions (different *uses* of the same word) rather than onomasiological *choices *(see Choice vs. use).

In this post I discuss ways in which we can plot intervals on **changes** (differences) rather than single probabilities.

The clearer our visualisations, the better we can understand our own data, focus our explanations on significant results and communicate our results to others. Continue reading “Change and certainty: plotting confidence intervals (2)”