Cycling and Self-Selection Bias

The Mail on Sunday reports on a self-selecting survey.

A Mail on Sunday article starts a headline with:

We will ditch Boris Johnson over bike lanes, say 27 percent of Tory voters

The claim derives from a self-selecting survey, run by FairFuelUK. The questions are likely to be leading for respondents. Recent surveys suggest around 2% of GB adults think transport is an important issue.

Self-selection bias

FairFuelUK is a campaign group, managed by motoring journalist Quentin Wilson.

It is not an independent market research company. Campaign groups running surveys often have two difficulties:

• Non-representative samples: Market research companies take great care to seek representative samples of the target population. Campaign groups may not take such care.
• Imbalanced questions: Writing questions is difficult. Research companies seek to measure public opinion, through balanced questions. Campaign groups may write questions which lead respondents to particular answers.

Representative survey samples look like the target population. Market research companies use quota and weights to ensure their samples are representative. There are also extra transparency rules through the British Polling Council.

The FairFuelUK Annual Road User Opinion Survey was an open access survey. The article…