Accuracy and reliability
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Division of Short Term Statistics, Department of Business StatisticsInger Hansen
+45 39 17 35 51
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Uncertainty is estimated to be relative small since data collection covers all enterprises operating trains on the Danish rail network.
Passenger transport have larger uncertainty than goods transport since the statistics for passenger transport are based on the companies' models of total number of passengers.
Only minor revisions are done to the first preliminary publication.
Overall accuracy
It is the assessment that the precision of the main indicators of the statistics - transport of passengers and goods - are within a 5 per cent band. But it is not possible to measure.
The main uncertainty is within passenger transport that is based on the passenger models of the operators in which besides sold tickets, passengers with season tickets and passengers without tickets are estimated as well.
There is no reason to believe that there is systematic bias in the statistics since all operators are reporting.
Sampling error
Not relevant to this statistics.
Non-sampling error
No errors occur due to errors in coverage, measure, missing data, etc.
All operators are reporting quarterly and there are no reason to believe that there should be any systematic errors in their reporting.
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 quality is assessed to be high since all operators are included in the survey with a response rate of 100 percent. There is no need for imputation or enumeration.
Information on investments is assessed to be of very quality as the information originates from the financial statements of the enterprises.
Transport of goods are assessed to be of high quality. No major revisions are made and there is no bias in the revisions made.
Passenger transport are of good quality. In this area higher uncertainty exists since data are based on the passenger models of the operators that is based on ticket sale, sale of season ticket, ticket inspections and passenger counts. The models estimates all types of passengers including passengers without tickets. Data are often revised. No bias seems to be present.
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
The statistics are revised for 4-8 quarters in connection to dissemination of new quarters. The revisions are due to revised figures from the operator.
In connection to major revisions of the passenger models, major revisions in data older than two years can occur occasional.