Accuracy and reliability

Overall accuracy

Overall accuracy depends on on the sample size and on the number of conducted interviews., which vary from survey to survey. With a sample of approximately 1,500 persons and a response rate of about 65 pct., which has normally been achieved in the last few years, the statistical uncertainty is in 95pct. of the cases estimated ranged within +/- 3 percentage points. A change in an indicator should be greater than 5 percentage points to indicate a significant change.

Sampling error

At present an omnibus survey consists of a sample of about 1,500 persons, drawn from a population of persons aged 16-74 years residing in Denmark.

As it is not possible to interview all 1,500 persons, each completed interview is given a personal weight, which partly corrects the effects of non-sampling and non-response and partly ensures that if you sum up all completed interviews you end up with a number of persons in tables and analyses corresponding to a number of persons of the age between 16 and 74 years. The questions asked to the persons are being enumerated with this weight, as well as weighted figures are being used at calculations of percentages.

However, a number of variables do not concern the individual person, but the family he/she is living with.

In these cases each respondent who is answering is being given a family weight, which ensures that the families with different numbers of persons aged 16 years or over are represented in the sample with varying probability. A family is defined as one or several persons between 16 and 74 years who live in the same accommodation and are related (includes also cohabiting couples) and their children, though there can only be one married or cohabiting couple in the family. The sum of the family weight for all completed interviews, gives the number of families in Denmark that have persons aged between 16 and 74 years. The number of families is thus an estimate for the random test.

With a sample of approximately 1,500 persons and a response rate of about 65%, which has normally been achieved in the last few years, the statistical uncertainty is in 95% of the cases estimated ranged within +/- 3 percentage points.

Non-sampling error

Not available information.

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

As it is not possible to interview all 1,500 persons, each completed interview is given a personal weight, which partly corrects the effects of non-sampling and non-response and partly ensures that if you sum up all completed interviews, you end up with a number of persons in tables and analyses corresponding to a number of persons of the age between 16 and 74 years. The questions asked to the persons are being enumerated with this weight, as well as weighted figures are being used at calculations of percentages.

However, a number of variables do not concern the individual person, but the family he/she is living with.

In these cases each respondent who is answering is being given a family weight, which ensures that the families with different numbers of persons aged 16 years or over are represented in the sample with varying probability. A family is defined as one or several persons between 16 and 74 years who live in the same accommodation and are related (includes also cohabiting couples) and their children, though there can only be one married or cohabiting couple in the family. The sum of the family weight for all completed interviews, gives the number of families in Denmark that have persons aged between 16 and 74 years. The number of families is thus an estimate for the random test.

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

Only final figures.