The Government Statistician decided that, for electoral purposes, Statistics New Zealand should impute Māori descent status for individuals not responding Yes or No to the Māori descent question in the 1996 Census of Population and Dwellings. Imputation is the allocation of a response based on the responses of others with similar attributes.
Imputation provides a sounder basis for electoral population calculations than the approach used in 1994, when all who did not specify a clear Yes or No answer in the 1991 Census were effectively allocated to not being of Mäori descent.
For the purposes of imputation, the key variables related to the Māori descent variable were identified using a statistical technique called CHAID (Chi-squared Automatic Interaction Detector). The imputation took place within subgroups created by cross-classification on the categories of the five variables identified – island, iwi, Māori ethnic group, Māori descent composition of the rest of the household, and age group. Within each subgroup, the proportions of those who specified a Yes or No response for Māori descent were used to allocate the remainder to Yes or No.
The effect of the imputation was to increase the proportion of those allocated to Māori descent from 16.0 percent to 17.4 percent of the total population. However, those imputed were allocated to Māori descent in a lower proportion than the proportion with Māori descent within the population who did specify Yes or No.
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