When different sub-groups are compared in respect of a variable on which age has an important influence, any differences in age distributions between these sub-groups are likely to affect the observed differences in the proportions of interest. For this reason, all Scottish Health Survey analyses by socio-economic variables ( NS-SEC (National Statistics Socio-Economic Classification), household income and SIMD (Scottish Index of Multiple Deprivation)) are age standardised.
It should be noted that all analysis in the published reports are presented separately for men and women. On some occasions, data for all adults is also presented (from 2009 survey onwards). All age standardisation was undertaken separately within each sex, expresssing male data to the overall male population and female data to the overall female population. When comparing data for the two sexes, it should be remembered that no age standardisation was introduced to remove the effects of the sexes' different age distribution in the sample.
Age standardisation was carried out, using the direct standardisation method. For the Scottish Health Survey 2009 the standard population to which the age distribution of sub-groups was adjusted was the mid-year 2009 census household population estimates for Scotland. For the Scottish Health Survey 2008, this was adjusted to the mid-year 2008 census household population estimates for Scotland, while for the Scottish Health Survey 2003 this was adjusted to the mid-year 2003 census population estimates for Scotland. All age standardisation has been undertaken separately within each sex.
Age standardisation was carried out using the age groups: 16-24, 25-34, 35-44, 45-54, 55-64, 65-74 and 75 and over.
Full details of how the age-standardised proportion was calculated, analysis by NS-SEC and by household income is available in the Scottish Health Survey Technical Report.
Using SAS/SPSS to age standardise data
We have produced examples of how to age standardise Scottish Health Survey data using the 2008 survey data. This includes the SPSS syntax and SAS code plus corresponding output generated. Click on the downloads below.
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