The Age standardized incidence rates are calculated first by estimating the age-specific rates and then applying these rates to the reference population , which is the standard world population. This process, called the direct standardisation is shown in table. This table calculates the age standardized incidence rates for stomach cancer among Danish males, 1988-92. The standard world population is the reference population here.
Lets look at the table.
If one wants to calculate the Age standardized incidence rate of tongue cancer in the Algerian females 1997-99. Divide d by y for every age group. Please note that if the numbers of cancers are little then the incidence rate can be expressed per 1 million standard world population instead of the more commonly used per 100,000 - world population. This has been done in the Swedish studies of the Malignant Oral Tumours. Parkin D.M. et al.