NHS Focus on Geography Series

About the data

Confidentiality disclosure control for the National Household Survey (NHS)

Disclosure control rules have been applied to data tables available from the National Household Survey (NHS). The number of actual records used to derive any number in a table must meet a minimum criterion. For a table cell where this criterion is not met, the number is replaced by a zero. Due to this disclosure control, subtotals will not necessarily aggregate to the total. As well, users should note that random rounding has also been applied to the data.


Rankings for selected variables:

Data tables or information relating to rankings (e.g., top 3 or top 5) may not be available for all levels of geography due to low counts, since ranking of information is only available for counts greater or equal to 15. In other cases, more information may be provided for specific geographies due to counts being tied at a given rank (e.g., four categories are shown in a top three ranking).


Random rounding and percentage distributions:

To ensure the confidentiality of responses collected for the 2011 National Household Survey while maintaining the quality of the results, a random rounding process is used to alter the values reported in individual cells. As a result, when these data are summed or grouped, the total value may not match the sum of the individual values, since the total and subtotals are independently rounded. Similarly, percentage distributions, which are calculated on rounded data, may not necessarily add up to 100%.

Due to random rounding, estimates and percentages may vary slightly between different 2011 National Household Survey products, such as the analytical documents and various data tables.

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