Sampling frame coverage and domain adjustment procedures for internet surveys

The objective of this paper is to define and compare alternative sampling frames for the representative population coverage as a basis for sample selection in internet surveys. The study aims to provide a methodology for domain weighting and adjustment procedures for free access web surveys that are based on the restricted access surveys. Some basic variables can be proposed for the data adjustment, namely gender breakdown, age groups, and education groups. The application of our work consists of a first stage based on a web survey by an e-mail invitation (restricted access) and a second stage based on a voluntary participation web survey (free access). An advertising company's registered customer list was taken as the sampling frame population for the first stage. This frame was an electronic e-mail list of the population of registered customers. Two different types of questionnaire were loaded on the company's internet web site for a month each, for two independent rounds, for testing the visual aspects of the questionnaire design. The restricted access internet survey design relies on probability selection procedures in this study. These results are used with the provided algorithms for the adjustment procedures of free access web surveys. A new methodology is also proposed for the estimation and allocation of the population frame characteristics of adult internet users by gender and age groups. The proposed alternative methodologies will be beneficial tools for future web survey users