The method of data collection, e.g. face to face interview, telephone interview or self-completion questionnaire, can affect survey estimates and should be reported.
The data collection form should include a question asking the respondent what their height is. For example, the Australian Bureau of Statistics National Health Survey 1995 included the question 'How tall are you without shoes?'. The data collection form should allow for both metric (to the nearest 1 cm) and imperial (to the nearest 0.5 inch) units to be recorded.
If practical, it is preferable to enter the raw data into the database before conversion of measures in imperial units to metric. However if this is not possible, height reported in imperial units can be converted to metric prior to data entry using a conversion factor of 2.54 cm to the inch.
Rounding to the nearest 1 cm will be required for measures converted to metric prior to data entry, and may be required for data reported in metric units to a greater level of precision than the nearest 1 cm. The following rounding conventions are desirable to reduce systematic over-reporting (Armitage & Berry 1994):
NNN.x where x < 5 - round down, e.g. 172.2 cm would be rounded to 172 cm.
NNN.x where x > 5 - round up, e.g. 172.7 cm would be rounded to 173 cm.
NNN.x where x = 5 - round to the nearest even number, e.g. 172.5 cm would be rounded to 172 cm, while 173.5 cm would be rounded to 174 cm.
Comments:
This metadata item is recommended for persons aged 18 years or older. It is recommended for use in population surveys when it is not possible to measure height.
It is recommended that in population surveys, sociodemographic data including ethnicity should be collected, as well as other risk factors including physiological status (e.g. pregnancy), physical activity, smoking and alcohol consumption. Summary statistics may need to be adjusted for these variables.
Metadata items currently exist for sex, date of birth, country of birth, Indigenous status and smoking. Metadata items are being developed for physical activity.
Presentation of data:
Means, 95% confidence intervals, medians and centiles should be reported to one decimal place. Where the sample permits, population estimates should be presented by sex and 5-year age groups. Estimates based on sample surveys may need to take into account sampling weights.
For consistency with conventional practice, and for current comparability with international data sets, recommended centiles are 5, 10, 15, 25, 50, 75, 85, 90 and 95. To estimate the 5th and 95th centiles, a sample size of at least 200 is recommended for each group for which the centiles are being specified.
For some reporting purposes, it may be desirable to present height data in categories. It is recommended that 5 cm groupings are used for this purpose. Height data should not be rounded before categorisation. The following categories may be appropriate for describing the heights of Australian men and women, although the range will depend on the population. The World Health Organization's range for height is 140-190 cm.
Height <140 cm
140 cm = Height < 145 cm
145 cm = Height < 150 cm
... in 5 cm categories
185 cm = Height < 190 cm
Height => 190 cm
On average, height tends to be overestimated when self-reported by respondents. Data for Australian men and women aged 20-69 years in 1989 indicated that men overestimated by an average of 1.1 cm (SEM* of 0.04 cm) and women by an average of 0.5 cm (SEM of 0.05 cm) (Waters 1993). The extent of overestimation varied with age.
