Patrick Sturgis, Professor of Research Methodology at the University, chaired the independent inquiry set up to investigate inaccuracies in the opinion polls during the 2015 general election campaign. The inquiry released its preliminary findings in January.
The independent inquiry was set up last May by the British Polling Council (BPC) and the Market Research Society (MRS). It was tasked with establishing the extent of inaccuracies in the polls, the reasons for inaccuracies, and whether the polls were adequately communicated to the general public.
Following in-depth investigations, the Inquiry panel concluded that the primary cause of the failure of the 2015 pre-election opinion polls was unrepresentativeness in the composition of the poll samples. The methods of sample recruitment used by the polling organisations resulted in systematic over-representation of Labour voters and under-representation of Conservative voters. Statistical adjustment procedures applied by polling organisations were not effective in mitigating these errors.
“There have been many theories and speculations about what went wrong in 2015 but, having considered the available evidence, the inquiry panel has concluded that the ways in which polling samples are constructed was the primary cause of the polling miss,” says Patrick.
The Inquiry will make a number of recommendations to the BPC and MRS when it publishes its report in March.