Parslow RC, Hepworth SJ, McKinney PA (2003);
The aim of this study was to assess the accuracy of recall of use of mobile phones by consumers, when measured against the "gold standard" of phone network operator records.
The authors used a "convenience volunteer sample". They advertised their study to 6,678 staff at the University of Leeds and to approximately 30,000 staff of Leeds City Council, hand-delivered recruitment letters to 1,500 people in selected areas of Leeds, and placed advertisements in two regional newspapers (circulation 78.000 and 104,000) for 4 successive days. Despite this only 138 mobile phone users agreed to participate. The volunteers completed an initial questionnaire and signed a consent form that gave permission for the researchers to obtain data from the mobile phone network operators. During the next 6 months (June 2000-March 2001) data were received from the network operators. At the end of the 6 months, the consumers were asked to complete a questionnaire that was based on the INTERPHONE study (an international case-control study under the auspices of IARC). In this they were asked to estimate their phone use for the previous 6 months, including number of calls made and their duration.
Questionnaires and operator data were available for 93 volunteers. Number of calls were grouped into high, medium, or low use according to the operator data (3, 3-8, >8 calls per week), and duration of calls (<4, 4-12, >12 minutes per week). There was only moderate agreement between self-report of use and operator records. The consumers showed a trend towards over-reporting call numbers and duration.
The results of this study may be subject to bias because of the very low participation rate. Only 93 volunteers took part from a potential pool of many thousands. In addition, 65 of these volunteers made less than 8 calls per week, a number that seems very low and inevitably raises questions about how typical the volunteers were of mobile phone users in general.