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Methods of statistics

What are official statistics?

Official statistics are statistics produced by government departments to:

  • Shed light on economic and social conditions.
  • Inform the development, implementation and monitoring of policies.
  • Inform decision making, debate and discussion within government and the wider community on economic and social issues.

Government and its administrative arms need official statistics for policy development, implementation and evaluation. The public also have similar information needs in order to evaluate government policy, to ensure public accountability, and to be adequately informed about social and economic conditions.

Objective, reliable and accessible official statistics give people confidence in the integrity of government and public decision making. Hence, in producing official statistics, it is important that the relevance, reliability and integrity of official statistics is maintained, and is perceived as such. It is also important that co-operation from respondents and providers of information is maintained, and that information given on a confidential basis remains so.

The range of New Zealand official statistics is wide, covering all key areas of national activity and life. The majority of the country's official statistics are produced by Statistics New Zealand which, over the years, has established policies and processes for achieving a high degree of public confidence in the objectivity and reliability of the statistical information it releases. The main official statistics produced by other departments – from surveys conducted by them or outsourced, or from administrative records – relate to crime, health and education.

The Statistics Act gives the Government Statistician responsibility for ensuring that all official statistics are produced using methodologies and practices that are statistically correct and that will provide outputs in which users can have confidence.

Official statistics are only useful if they are relevant to conditions and issues prevailing at the time. For this reason advisory groups are often set up to provide expert advice on any changes required to the official statistics that are produced. As required by section 7(1) of the Statistics Act 1975, the Government Statistician from time to time reviews the collection, compilation, analysis, abstraction, and publication of official statistics prepared by Statistics New Zealand or by other government departments.

To ensure members of the public have access to important key statistics, the main findings of a set of official statistics are usually made available through the media or main public libraries. Requests for specific information may be produced on a commercial basis to meet the needs of one organisation.

The New Zealand official statistical system relies on the long-standing co-operation of New Zealand's citizens and its businesses, government agencies and other organisations. Accurate and timely statistical information could not be produced without their continued co-operation and goodwill.

How are official statistics produced?

Official statistics are compiled in accordance with standards and procedures that help to make the data robust and comparable with statistics produced from other sources, both within New Zealand and internationally.

In presenting the information international frameworks are often used to summarise the data and to show connections between components. For example, Balance of Payment statistics are presented in a format consistent with the international standards issued by the International Monetary Fund (IMF) – New Zealand is in the process of adopting the Balance of Payments Manual fifth edition series. The presentation of New Zealand's National Account statistics follows the recommendations of the United Nations System of National Accounts.

A comprehensive set of New Zealand classifications and standards are also used in the production of official statistics. These cover both economic and social statistics, are based wherever possible on international standards, and are aimed at ensuring consistency and uniformity in official statistics. The standards and classifications are periodically reviewed and updated, ensuring that the statistics produced are relevant while maintaining a continuity with earlier statistical series.

Official statistics are also compiled in accordance with a number of policies, protocols and guidelines. Statistics New Zealand has developed a series of Protocols for Official Statistics to ensure official statistics, regardless of the supplier, are produced using statistically sound methods and practices.

Quality measures

From the design to the dissemination stage of a statistical collection there are many ways in which errors can be introduced into the results.

Some errors (eg those resulting from the use of sampling) are random and their magnitude measurable. This sample error is the expected difference you get from survey results compared to surveying the whole survey population. Statistics New Zealand calculates the sample errors to provide users of such statistics with information on the magnitude of these errors.

Errors can also occur as a result of the survey method itself, for example non-response. This type of error is known as non-sampling error. Statistics New Zealand tries to minimise the extent of non-sampling error by such practices as ensuring that responses are obtained from everyone selected in a sample, particularly the key respondents. We also strive to ensure that the population we are reporting on is actually surveyed – for example our household and business surveys cover all areas of New Zealand from Cape Reinga to Stewart Island.

To minimise error, all our questionnaires are carefully designed and tested to make them easy for respondents to understand and complete correctly. During the processing of statistics, checks are carried out to ensure the data appears consistent. Checks are also undertaken to make sure responses have been recorded correctly. Care needs to be taken when releasing data with high errors. 

Record of Statistical Collections and Methods

Statistics New Zealand has compiled a comprehensive set of metadata about the methods used in the production of each specific statistical collection and output. This metadata includes information on changes that have occurred over time.

Links to Related Material

Data Integration Manual 
Producers Price Indexes - Concepts, Sources and Methods 
Seasonal adjustment within Statistics New Zealand

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