Comparing mobile with fixed phones for surveys
A number of studies have looked at the differences between responses from mobile and fixed-lined phones. One study20 targeted at Portuguese adults (aged 15 years and over), focused on internet usage, attitudes towards the internet, cultural practices and demographics. Two surveys were conducted by the same survey company in order to overcome problems that might confuse the assessment of survey results if multiple sources of data collection were used. There were no conclusive results regarding the performance of mobile phone surveys as opposed to fixed phone surveys in terms of response rates. However, there were several features of mobile phones that could induce lower overall response rates. First, a mobile phone was seen as a personal device and many users may consider receiving a call from strangers on their mobile phone an invasion of their privacy. The reaction may be a refusal or even a hang-up-without-answering as soon as they see an unfamiliar number on the phone screen. Second, the participant may be more or less willing to cooperate depending on the tariff that has been contracted for the mobile phone. Charging for receiving calls may discourage the acceptance of some calls, namely those from unknown sources. Mobile phones have the advantage of making the person accessible at any time of the day because it is a personal device carried at all times.
A second study21 by Peter Lynn and Olena Kaminska from the University of Essex compared the impact of mobile phones on measurement errors in surveys compared to fixed-line phones. Only small differences in survey measures between the mobile phone interviews and the fixed phone interviews were found, but these differences indicate that data quality may be higher with mobile phone interviews. The paper suggests that an explanation is that survey respondents have greater control over whether other people are within earshot and whether others can listen in from another line. When on a fixed line, other people may be able to hear the responses, meaning that respondents may censor their responses to avoid socially undesirable answers.