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Accuracy and reliability

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Business Development, Business Statistics
Mahtab Keshavarz
+45 39 17 31 15

mke@dst.dk

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Computer Services

Overall, the uncertainty of the level of the total turnover is estimated below 1 per cent. The uncertainty varies widely between services. In some services the uncertainty is significantly higher than the uncertainty of the total turnover.

Overall accuracy

For the reference year 2020 there are 1052 enterprises in the sample, covering 90 per cent of the total turnover in FRAME for the sector for Computer Services. 985 enterprises answered the questionnaire, i.e. the response rate is 94 percent. The usable questionnaires are from 976 enterprises. There is a lapse of 7 per cent. The lapse are due to wrong industry code and closure of the enterprises and non-responded questionnaires.

The usable data from 976 enterprises grossed up to the total level (the target population) of the 6-digit industries within the sector for Computer Services by using preliminary turnover from the Business Register. Each company is assigned a weight, that corresponds to the ratio of population and responses in a given size group and industry. The enumeration is made by ratio estimation.

As the survey is random, the figures can be associated with some statistical uncertainty in the form of random variation. The sampling error is calculated for all services in the form of variance, 95 pct. confidence interval and coefficient of variation Uncertainty estimates can be seen in the attached document usikkerhedsestimater_IT.

The figures for 2019 are preliminary and will not revised in the national publishing. For delivery to EU the figures are calculated (revised) based on Accounts Statistics.

Sampling error

The sample was drawn at 1758 consisting of 1052 enterprises. Of these, 985 companies have completed the questionnaire, i.e. the response rate is 94 percent. The usable questionnaires were from 976 enterprises.

The sampling error is calculated for all services in the form of variance, 95 pct. confidence interval and coefficient of variation Uncertainty estimates can be seen in the attached document usikkerhedsestimater_IT.

Non-sampling error

The total uncertainty consists of sampling uncertainty and other systematic uncertainty. In other uncertainties include inter alia measurement error and non response error/lapse.

Coverage error: The population is defined by the industry, the enterprises registered in the Business Register by themselves. Errors of classification of the industries will be expected. This means that there may be enterprises in the population that really should not be classified as an enterprise in the sector Computer Services, but also companies in the sector Computer Services can be classified with the wrong industry.

In the context of fault tracing and quality assurance of the statistics, number of these errors continuously are found and corrected. Companies that incorrectly classified as Computer Services cause over-coverage while misclassifications within Computer Services cause over-coverage in one industry but under-coverage in another. These coverage error is detected primarily for companies in the sample, but also in some cases for non-sampled companies.

Under- coverage in the form of companies that are classified entirely outside Computer Services, even though they should properly be classified as Computer Services, are difficult to detect, but can be found also. The significance of these coverage problems are generally small because the volume is estimated to be small.

The total number of enterprises in the FRAME population is estimated at approx. 1.758, and among these the sample is selected. The sample for the reference year 2020 was 1052 companies and is thus approx. 60 per cent. of the FRAME population. Because of the stratified selection, where large companies are more likely to selection than the smaller, the sample consists 90 per cent. of the total turnover of the FRAME population.

Measurement error: Uncertainty due to lapse, incorrectly reported numbers and misunderstandings has sought to minimize by repeated reminders by non-reporting, as well as by substantial verification of the reported figures.

Generally the services in the questionnaire are based on Statistical Classification of Products by Activity CPA CPA 2008, with an adjustment to Danish conditions. It can be an uncertainty in the distribution of turnover and export by services when the services CPA 2008 are not quite commensurate with the classification of products of the firms.

Non response error: There are 1052 enterprises in the sample. The usable questionnaires are from 985 enterprises, i.e. there is a lapse of 7 per cent.

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

It can be problems in comparing figures over time. This is because the questionnaire has been revised a few times since 1995. Moreover, there are break of data due to the changes in industry codes (from NACE rev.1 to NACE rev. 1.1 and to Nace rev. 2).

From the reference year 2013 the method is changed so the enumeration is based on a new data from the Central Business Register. Data are back calculated for 2012. Which means that the results before the year 2012 are not directly comparable to the results from 2012 onwards.

For the reference year 2020 there are 1052 enterprises in the sample, covering approx. 90 per cent of the total turnover in FRAME for the sector for Computer Services. 985 enterprises answered the questionnaire, i.e. the response rate is 93 percent. The usable questionnaires are from 985 enterprises. There is a lapse of 7 per cent. The lapse are due to wrong industry code and closure of the enterprises and non-responded questionnaires.

The usable data from 985 enterprises grossed up to the total level (the target population) of the 6-digit industries within the sector for Computer Services by using preliminary turnover from the Business Register. Each company is assigned a weight, that corresponds to the ratio of population and responses in a given size group and industry. The enumeration is made by ratio estimation.

As the survey is random, the figures can be associated with some statistical uncertainty in the form of random variation. The sampling error is calculated for all services in the form of variance, 95 pct. confidence interval and coefficient of variation Uncertainty estimates can be seen in the attached document usikkerhedsestimater_IT.

The figures for 2019 are preliminary and will not revised in the national publishing. For delivery to EU the figures are calculated (revised) based on Accounts Statistics.

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 published data will not be revised, since the statistics is published once a year.