Accuracy and reliability

Overall accuracy

The overall accuracy in the survey of the harvest of grain, peas and rape can be described as good. However, there is some uncertainty for crops grown in small regions at national level, particularly with regard to spring rape.

For coarse fodder and root crops, reliability must be considered reasonable for average yields, while it is high for area information.

The reliability of the forecast for winter areas must generally be described as less good than the harvest survey.

Sampling error

The harvest of cereals, rape and peas and pulses

Sample of approximately 2,800 farms (about 8 per cent of all farms). The response rate in the survey is generally over 95 per cent, and does not raise significant uncertainty.

The coefficient of variance of the total harvest of cereals, rape and pulses is about 0.3 per cent., corresponding to about 30,000 tons. grain. For crops with limited distribution, the uncertainty is typically up to 5 per cent.

The statistical uncertainty meets the quality requirement in EU act on harvest statistics.

Because of greater spread in the use of straw than in crop yields, the uncertainty of straw use for different purposes is relatively larger than the uncertainty harvest of cereals, rape and peas.

Harvest of coarse fodder

The response rate in the study of forage harvest is somewhat smaller than 100 per cent., which is a source of uncertainty.

Areas planted with winter crops

No sampling errors as such. The ratio of the areas in the forecast and recent areas recorded indicates an uncertainty of the order of 5 per cent of the total areas with winter seed.

Coefficient of variance (CV) for the main variable in 2017

The harvest of cereals, rape and peas and pulses

Production

• Total cereals 0.3
• Winter wheat 0.3
• Spring wheat 1.6
• Rye 0.9
• Triticale 2.2
• Winter barley 0.6
• Spring barley 0.4
• Grain maize and corn cob mix 4.4
• Oats and mixed grain total of 1.3
• Havre 1.3
• Mixed grain 4.7
• Rape, total 0.6
• Winter rape 0.6
• Spring rape 14.3
• Pulses 4.6
• Field peas 4.6

Non-sampling error

Applications for EU support are the base for the study of the harvest of grain, etc. Since only a small proportion of farmers have production without EU support the coverage of the target population is assumed to be accurate.

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 overall accuracy in the survey of the harvest of grain, peas and rape can be described as good. However, there is some uncertainty for crops grown in small regions at national level, particularly with regard to spring rape.

For coarse fodder, reliability must be considered reasonable for average yields, while it is high for area information.

The reliability of the forecast for winter areas must generally be described as less good than the harvest survey.

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

Provisional results for harvest of cereals, pulses and rape seed are in line with final results published later on.

Other results are only prepared once every year, and consequently provisional and final figures cannot be distinguished.