assistance).
If the target population is the general population (households or individuals), there is a problem with the sampling frame. Some countries have a population register. Such a register contains addresses. Therefore, use it as a sampling frame for a face‐to‐face or mail survey. Sometimes telephone numbers link to addresses, which makes it possible to use it as a sampling frame for telephone surveys. Unfortunately, these registers do not contain e‐mail addresses, nor can e‐mail addresses link to it.
Internet penetration varies greatly between countries (see Chapters 1 and 10 about under‐coverage problems). Presently, Internet coverage is relatively high, say, between 60% and 90% in a number of European countries. These coverage rates seem to suggest that general population web surveys are possible in these countries and that they can compete with traditional data collection modes. However, note that a large Internet penetration does not imply high Internet use. Moreover, it also does not imply high quality if fast Internet connections are available. For example, not everyone with Internet access has broadband.
One should always bear in mind that not everyone has access to the Internet. One example is that not every employee of a company is allowed to use the Internet. Moreover, Internet access is substantially lower in many countries for specific subpopulations. For example, Hispanic blacks are underrepresented in the United States. Another example of underrepresented groups are people with low education and people living in rural areas. This situation exists in many countries. The elderly, also, are often underrepresented among Internet users. Under‐coverage leads to web surveys that lack of representativity. Therefore, there is a risk to draw wrong conclusions from the survey results.
If the target population consists of businesses, it is quite probable, in most countries, that each business has Internet access and therefore has an e‐mail address. Thus, the collection of business to sample for a web survey is rather close to the target population. However, obtaining a complete list of e‐mail addresses for businesses may be a very difficult task. Partial lists sometimes exist, but complete lists are often lacking. NSIs regularly contact large enterprises for surveys. Therefore, they may have a complete list of e‐mail addresses of certain economic branches or specific size classes of companies. In most cases, obtaining an e‐mail population list for small enterprises and businesses could well be a difficult task for NSIs. Even if such a list is available, it requires a lot of effort to maintain it. In European countries, the maintenance of the business register—requested from Eurostat—allows for the updated list of businesses and their stratification variables and address (e‐mail address, in most cases). NSIs are now going to run many surveys via web. Even census data collection is on the web, thus sharing many methodological problems with the web surveys.
If the target population is a closed population (employees of a company or students of university), often there is a sampling frame containing e‐mail addresses of all members of the population. In such situations, there is no difference between the target population and the sampling frame. There are no coverage problems. This is the ideal case for a web survey.
With respect to the survey administrator, differences may occur with respect to the amount of information for setting up the surveys and the topics that are addressed in the web survey. NSIs and official statistics bodies probably have the largest amount of information available on the general population (households and individuals) and businesses (or institutions). They may have access to population registers, they may have census data, and they may manage demographic databases, the business register, and other sources of information. Therefore, although this huge amount of data may be insufficient for generating a sampling frame of e‐mail addresses for the target population, they may well be in a rather good position to obtain this information. This is happening in the near future, since the trend in the diffusion of web surveys is gaining importance and the Internet penetration within the population continues to increase. Currently, the advantages of the NSIs are twofold:
They often have a sampling frame for the general population of individuals of households based on addresses. This means that they are able to select a suitable probability based sample from the target population. They can contact the selected persons/households using an alternative mode (for example, by mail) while using the web mode as a second step in the data collection process.
As regards businesses, they have a full population list, at least for large businesses, together with contact points and, probably, e‐mail addresses. Therefore, a sampling frame adequate for web is available.
Example 2.2 describes how Statistics Netherlands has managed to use the available information to gain insights on the web participation of the population.
EXAMPLE 2.2 The ICT survey pilot
Statistics Netherlands carried out a pilot with the ICT survey to find out whether it was possible to use the web for data collection. This survey collects information on the use of computers and Internet in households and by individuals. The regular ICT survey was a CATI survey. It was rather expensive. It also suffered from under‐coverage because the sample selection was from the telephone directory. It was not possible to select households with unlisted numbers and mobile‐only households.
The sample selection for the pilot was from the population register. Therefore, there was no under‐coverage. All persons in the sample received an invitation letter by mail. The letter contained the Internet address of the survey and a unique login code. Respondents had the possibility to complete the questionnaire on paper. To prevent those with Internet to respond by paper, the paper questionnaire was not included in the invitation letter. People had to apply for the paper form by returning a stamped return postcard.
After one week, a postcard was sent to all nonrespondents with a reminder to complete the survey questionnaire, either by web or mail. Two weeks after receipt of the invitation letter, the remaining nonrespondents were approached again. Part of these nonrespondents received a reminder letter, and another part was called by telephone (if a telephone number was available). The telephone call was just to remind the nonrespondents and did not replace the paper/web questionnaire form.
It turned out the postcard reminders worked well. Each time they were sent, there was a substantial increase in response. The telephone reminder did not work as well as the postcard reminder. Of the people that promised by telephone to fill in the form, only 40% actually did so.
For the survey administrator, a favorable environment for running web surveys is a closed population. For example, businesses or institutions' administrative database records for each employee contain individual data and corporate e‐mail address.
It is a similar situation for the universities. The university database records the student's e‐mail address (the institutional one and—sometimes—the private one).
Business customer's databases record detailed information on each customer including contact references, among them e‐mail addresses.
Other survey administrators, such as academic researchers, market research companies, or private businesses, may not have proper sampling frames available. One solution of this problem could be to let an NSI select the sample for them. Another could be to obtain a copy of the sampling frame after privacy‐related information has been removed. Nevertheless, privacy‐related laws may prevent NSIs to make available sampling frame information to third parties.
With
