What are direct estimates? Why are there differences between the direct estimates and the estimates from the model?
The direct estimates are constructed based only on the survey data and the design weights for the sample in the small areas of interest. When the sample sizes are small, the direct estimates are unreliable. The model-based estimates are based on an explicit statistical regression model which combines the direct estimates and information from auxiliary data on small areas obtained from a variety of external sources. The model-based estimates are generally more reliable and stable assuming that the data fit the model reasonably well. However, when there is not much local data for a particular area, the model-based estimates rely on the relationship between the auxiliary data describing the characteristics of the area and the response variable of interest, e.g., the relationship between median family income and smoking prevalence at the county level.
