Читать книгу Handbook of Web Surveys - Jelke Bethlehem - Страница 57

In the construction of the termed PAADEL (Agro‐Food and Demographic Panel in Lombardy), the steps described in the flowchart (Figures 3.1 and 3.2) were followed. This section examines some problems that arise at the different steps and the interrelationship between errors. In particular, focus is on the step of choice of the mode and on the use of adaptive design during the step of the data collection.

Skipping the first two steps (Deciding the objective, Metadata description, and Designing the survey), which are related to the survey's subject matter and beyond the present study's scope, focus should shift to the mode choice. The panel's objective was to have a probability‐based web data collection. Target population were Lombardy region inhabitants. Internet penetration in the population was not high, and an exhaustive list of e‐mail addresses did not exist; thus, there was a need for a proxy for the population list. The proxy list available contained postal addresses and phone numbers. Therefore, a probability‐based survey was not possible without some preliminary step to select a probability‐based sample; the adoption of a mixed‐mode approach to cover the part of the population not on the Internet was the solution. Thus, a contact mode had to be decided, considering that postal and telephone number codes were available. The selection of the survey mode for the sampled units took place using a mixed‐contact mode, partially telephone and partially mail. The survey mode was a mixed‐mode as well; only part of the sampled units had an e‐mail address and accepted a web survey, while for some others the interview was by telephone or mail.

Table 3.2 Responses to the survey by mode and percentage composition

Mode	%	Mode	%
Web	68.5	Web	45.5
Phone	71.2	Phone	30.2
Mail	53.2	Mail	24.3
Total	63.5	Total	100.0

The data collected by mode are in Table 3.2. The response rate has been satisfactory. The web mode turned out to be the most important component of the mixed‐mode approach.

To address the web component of the mixed‐mode approach, the steps in Figure 3.1 were followed.

To show how to use, at the monitoring data collection step, adaptive design to increase the response rate in a web survey and how different error types are interrelated, Bianchi and Biffignandi (2014) applied experimental responsive design strategies, in retrospect, to the recruitment of the mixed‐mode panel. Especially targeting the units contributing the most to nonresponse bias during data collection was useful. The identification of such units took place through indicators representing proxy measures for nonresponse bias. In their study, the authors adopted three strategies, and the results show that the method proves promising in reducing nonresponse bias. When evaluated in the TSE framework, i.e., considering how different errors relates to the adopted responsive strategies, the results are not uniform across variables. In general, there is a reduction of total errors.