Accuracy and reliability

Overall accuracy

Equivalent to other surveys based on samples the results of this survey have some sampling errors attached. The sampling errors are related to the sample selection and the patterns of non-response. Non-response occurs when an interview with a selected person is not carried out. Non-response increases the inaccuracy rate because the probability of conducting an interview with all selected people is uneven. In other words, it is the same kind of sections of the populations where interviews are not being carried out at the same extent as other sections of the population. Consequently the level of representatively is affected.

In the AES survey it was decided to apply intervals of confidence at a 95 significance level. The uncertainty has been calculated for participation in formal education and participation in courses.

For tables based on break-downs of various variables it can occur that the result is based on very few respondents. This means that the re-scaling to the total population can sometimes be based on very few respondents. Consequently, the tables must be looked upon with an additional uncertainty compared to results based on a larger number of respondents.

Sampling error

The sampling error is calculated as an interval of +/- around an estimated value, usually expressed by 95 pct. confidence level.

Non-sampling error

Apart from coverage errors related to sex and age groups no estimations have been conducted in relation to other uncertainties than sampling errors. In surveys like this also errors arising by the respondent's misunderstanding of questions or concepts are present. For interviews conducted as telephone interviews these types of error are limited.

Quality management

Statistics Denmark follows the recommendations on organisation and management of quality given in the Code of Practice for European Statistics (CoP) and the implementation guidelines given in the Quality Assurance Framework of the European Statistical System (QAF). A Working Group on Quality and a central quality assurance function have been established to continuously carry through control of products and processes.

Quality assurance

Statistics Denmark follows the principles in the Code of Practice for European Statistics (CoP) and uses the Quality Assurance Framework of the European Statistical System (QAF) for the implementation of the principles. This involves continuous decentralized and central control of products and processes based on documentation following international standards. The central quality assurance function reports to the Working Group on Quality. Reports include suggestions for improvement that are assessed, decided and subsequently implemented.

Quality assessment

For sample based surveys the results have some sampling errors involved. The sampling errors are related to the sample selection and the patterns of non-response. Non-response occurs when an interview with a selected person is not carried out. Non-response increases the inaccuracy rate because the probability of conducting an interview with all selected people is uneven. In other words, it is the same kind of sections of the populations where interviews are not being carried out at the same extent as other sections of the population. Consequently the level of representatively is affected. The register used for sampling has a total coverage of persons.

The respondents were selected using stratified random sampling. The population was divided into three non-overlapping strata, and samples were selected from each stratum independently. The three strata are defined by the age groups.

Data revision - policy

Statistics Denmark revises published figures in accordance with the Revision Policy for Statistics Denmark. The common procedures and principles of the Revision Policy are for some statistics supplemented by a specific revision practice.

Data revision practice

Final figures are published.