Home owners: what’s your SPF?
Home owners will be familiar with the wide array of security devices available to secure their homes, each more expensive than the last – from burglar alarms, security chains, sensor lights and deadlocks, to window bars and CCTV cameras. But what is the most effective combination of security devices? This was a question that a team of researchers, led by Professor Andromachi Tseloni, at Loughborough University, UCL and Simon Fraser University, Canada, set out to answer.
The team used 2008/09 and 2011/12 data from the Crime Survey of England and Wales, which has asked a random sub-sample of survey respondents about the use of security devices for several decades. Applying the Security Impact Assessment Tool (SIAT) methodology (developed and described by Farrell et al), the team compared the likelihood of burglary for populations without security, with a particular security device or combination of devices to the overall likelihood of burglary.
In a paper published earlier this year, Tseloni and colleagues explained: "This comparison results in odds ratios. Contrasting the odds ratios given the availability of a security device or combination of devices with respect to no security identifies the amount of protection conferred relative to no security. The resulting metric is termed the Security Protection Factor (SPF)."
Speaking at the Royal Statistical Society's International Conference today, Tseloni identified window locks and double locks/deadlocks as the most common combination of security devices. This combination has an SPF of 12.5, which means that homes with window locks and deadlocks are 12.5 times less likely to be at risk of burglary.
Adding external lights on a sensor to the window lock/deadlock combo bumped the SPF up to 34.4. But lowering the risk of burglary isn't always a straightforward question of adding more devices. The combination of external lights, internal lights on a timer, window locks, deadlocks and burglar alarms generates an SPF of 29.6. Drop the burglar alarm, however, and the SPF factor rises to 49.1.