Notes

1. The following conventions have been used in tables dealing with 'observed' data (that is, data not standardised or presented in ratio form: see note 8):

- No observations (zero value)

0 Non-zero values of less than 0.5% and thus rounded to zero

[ ] Used to warn of small sample bases, if the unweighted base is less than 50. (If a group's unweighted base is less than 30, data are normally not shown for that group.)

2. Because of rounding, row or column percentages may not add exactly to 100%.

3. A percentage may be quoted in the text for a single category that aggregates two or more of the percentages shown in a table. The percentage for the single category may, because of rounding, differ by one percentage point from the sum of the percentages in the table.

4. Values for means, medians, percentiles and standard errors are shown to an appropriate number of decimal places. Standard Error may sometimes be abbreviated to SE for space reasons, and Standard Deviation to SD.

5. 'Missing values' occur for several reasons, including refusal or inability to answer a particular question; refusal to co-operate in an entire section of the survey (such as the nurse visit); and cases where the question is not applicable to the informant. In general, missing values have been omitted from all tables and analyses.

6. The group to whom each table refers (for example, those providing a valid blood pressure measurement) is stated at the upper left corner of the table.

7. All minority ethnic group data relate to 1999. General population data normally relate to 1999, but because the general population sample in 1999 did not have a nurse visit (and because certain questions were asked only of minority ethnic groups), comparative data about the general population have in some cases had to be taken from the previous year (1998, or in the case of children 1997 because of the large child sample in that year). Where this has been the case, it is indicated.

8. Some tables and charts show data in the form of risk ratios or ratios of means. In all chapters except Chapter 13, these ratios have been age-standardised. In the charts, ratios have been plotted using a logarithmic scale on the vertical (y) axis. The range is normally from 0.1 to 10.0 (the general population being 1.0), though in certain charts the lower limit has been extended to 0.01. The lower and upper 95% confidence limits are also plotted, as a vertical line with markers at the lower and upper ends. If the line continues to the edge of the chart without such a marker, this is because the upper or lower limit is outside the range shown.

9. A mean or a risk ratio for a sub-group will be zero if no cases of the condition concerned occurred in that group. In such cases, the standard error cannot be estimated, and a dash has been inserted in the table. The standard error has also been replaced by a dash where both the mean or ratio and the standard error were rounded to 0.00.

10. The data used in the report have been weighted. The weighting is described in Chapter 14, Section 14.8, in Volume 2 of this report. Both weighted and unweighted sample bases are normally shown at the foot of the table. The weighted numbers reflect the relative size of each group in the population, not numbers of interviews made, which are shown by the unweighted bases.

11. The term 'significant' refers to statistical significance and is not intended to imply substantive importance.

We welcome your comments on this site. Prepared 10 January 2001