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STATISTICAL:
If individual values are similar within the areas (in statistic language: Think! Two identical twins are only one “statistical individual”….Isn’t it? In ordinary regression techniques two identical twins are two individuals, but in multilevel regression only one. Ordinary regression techniques overestimate the sample size giving smaller standard errors (the higher the samples size the lower the standard error). EPIDEMIOLOGICAL:
How much of the individual differences are between the areas (how much of the teeth
health variance is because of the mouths?)….1%?... 10%...50%?. This measuring of intra-class correlation.To know if individual associations vary between the areas (in statistic language: Area differences may differ for different individuals (in statistic language: |

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