2001 Census: Education 2001
Standards
Symbols
The interpretation of the symbols used throughout this report is as follows:
- nil or zero
-- amount too small to be expressed
.. figures not available
... not applicable
nfd not further defined
nec not elsewhere classified
C confidential
Confidentiality
The Statistics Act 1975 sets out strict requirements on Statistics New Zealand to protect the confidentiality of information obtained from respondents during the Census of Population and Dwellings and other surveys. Action is taken at every stage of the census to make sure that only authorised people work with individual returns, and then with only as much as they need to know for that stage of the process. All staff who work on the census and other surveys have signed a Declaration of Secrecy.
It is an offence for any staff member to break the statutory declarations of secrecy that they make, and there is a very long history and tradition of consistent performance with keeping confidences over many censuses. Such a record supports the high level of public trust in Statistics New Zealand, and has led to the high levels of response to the census by New Zealanders.
During the collection of documents, there were arrangements for forms to be collected in sealed envelopes, should that option be chosen by a household or person. The names and addresses of respondents were used to ensure that all forms were collected from a household and are not part of the final computerised information.
When the census paper forms have been processed, Statistics New Zealand continues to have clear, statutory obligations to maintain the confidentiality of the census data in its custody. The Statistics Act includes a section that overrides the legal investigative powers of other government agencies to obtain information. In publishing statistical tables and other aggregated statistics from the census datasets, Statistics New Zealand employs measures such as random rounding to protect the confidentiality of individual information.
Random rounding
Since the 1981 Census, Statistics New Zealand has utilised a confidentiality assurance technique of randomly rounding census statistics to base three. This enables the greatest possible amount of census data to be released without compromising the privacy of individual responses.
Under the random rounding process, all table cell values, including row and column totals, are rounded as follows:
- Zero counts and counts which are already multiples of three are left unchanged.
- Other counts are rounded to one or other of the two nearest multiples of three.
All rounding, including separate rounding of totals and sub-totals is carried out on the recorded results. The probabilities of rounding up or down are set so that the long run expected value equals the original count. For example, an original count of 17 would be rounded to 15 with a probability of 1/3 and rounded to 18 with a probability of 2/3, since 15 x 1/3 + 18 x 2/3 = 17. The effect of this rounding on the accuracy of census statistics for practically any proposed use is insignificant.
Rounding procedures
On occasions, figures or percentages have been rounded off to the nearest unit or decimal point. This may result in a total disagreeing with the total of the individual items as shown in tables.
Calculation of ratios
Unless otherwise stated, the 'not stated' category has been excluded from the denominator in calculation of ratios and percentages.