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Accuracy and reliability

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Statistics Denmark, Short Term Statistics
Simon B. Halifax
+45 3917 3088

sbh@dst.dk

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Retail Trade Survey

Regarding precision, sampling error is estimated to plus/minus 1-2 percentage points for the confidence indicators. The figures are by definition reliable, since they are not revised.

Overall accuracy

The statistics covers a substantial part of enterprises in the selected industries and is considered as statistically representative. In general, sampling error uncertainty at plus/minus 1-2 percentage point is expected for the indicators. Non-sampling errors are caused by non-response errors (about 24 pct. non responses), and especially missing responses from large companies may cause fluctuations from month to month. Also measurement errors influence the statistics. A senior person in the company is asked to check mark his perception of the developments over the past three months and his expectations for the next three months. The expectations are inherently uncertain. The perception of the development over the past may also be associated uncertainty, depending on the respondent's current level of information.

Sampling error

The survey variables are mostly categorical of the type increase, unchanged or decrease. For each month' statistics is calculated confidence interval with upper and lower values for the three variables constituting the Composite Confidence Indicator. The confidence interval varies from month to month, and depends on the actual number of responses in each answer category.

Non-sampling error

Basically the statistics is assumed to cover the target population satisfactory.

There is no systematically checking for errors.

By sample update, new enterprises may inform they are not registered in correct business sector and therefore not relevant.

Between lines of businesses there may be some over-coverage because of wrong or changed registration.

The tendency surveys are subjects to measurement errors: A senior person in the company is asked to check mark his perception of the developments over the past three months and his expectations for the next three months. The expectations are inherently uncertain. The perception of the development over the past may also be associated uncertainty, depending on the respondent's current level of 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

The statistics covers a substantial part of enterprises in the selected industries and is considered as statistically representative. In general, sampling error uncertainty at plus/minus 1-2 percentage point is expected for the indicators. Non-sampling errors are caused by non-response errors (about 24 pct. non-responses), and especially missing responses from large companies may cause fluctuations from month to month. Also measurement errors influence the statistics. A senior person in the company is asked to check mark his perception of the developments over the past three months and his expectations for the next three months. The expectations are inherently uncertain. The perception of the development over the past may also be associated uncertainty, depending on the respondent's current level of information.

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 data is published. However, since questions are targeting "next 3 month" and "past 3 month" it is possible to analyze if expectations for the next 3 month afterwards has been realized.