New Filter to Help You Interpret the Referendum Polls

It will come as no surprise to regular users of this site to hear that the most visited page is the referendum voting intention time series. This graph presents the results from all polls that have asked the question that will appear on this September’s ballot paper: ‘Should Scotland be an independent country?’

One strength of this graph is that it brings together polling data from all the different companies in one place. But we also know from user comments that it can be frustrating trying to interpret the data. What appear to be major changes from one poll to the next can sometimes just be a reflection of differences in polling methodology. In our blog, John Curtice regularly comments on how variation between companies can be a product of different methods of data collection, preambles to introduce the main question or different weighting techniques. On the other hand, when a company’s latest poll is compared with its predecessors a much more stable picture often emerges.

So to help you differentiate between real trends in public opinion and variation caused by the different approaches of the polling companies, we have developed a Filter which allows you to choose which companies’ figures you want to view. For example, you can now compare Ipsos Mori’s referendum polls  with ICM’s. If you view each company one at a time, you will see that there is less fluctuation in public opinion over time than one might assume from the graph with all polls included.

To use this functionality, just go to the referendum voting intention page or any polling question that has data from different polling companies.

1) Scroll down and you will see an option for ‘Filter by polling company’
2) Then tick the box beside the polling company(ies) whose polls you want to see and press ‘VIEW FILTERED POLLS’
3) The filter will then be applied until you press ‘Cancel’ or leave the page

You can still remove the ‘Don’t know’ responses and view the graph as a table or bar chart with the filter applied. Also if you click on ‘Notes and methodology for this question’ with a filter on, you will see that only the details relevant to the polling company or companies you have selected are now featured.

If you have any feedback on the new Filter please email us at or write a comment under this blog.

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