# BRFSS 2010 Weighting Formula

**FINALWT = STRWT * 1 OVER NPH * NAD * POSTSTRAT**

The computational formula above is intended to reflect all the possible factors that could be taken into account in weighting a state’s data. Where a factor does not apply its value is set to one.

**FINALWT** is the final weight assigned to each respondent.

**STRWT** accounts for differences in the basic probability of selection among strata (subsets of area code/prefix combinations). It is the inverse of the sampling fraction of each stratum. There is almost never a complete correspondence between strata, which are defined by subsets of area code/prefix combinations, and regions, which are defined by the boundaries of government entities.

**1/NPH** is the inverse of the number of residential telephone numbers in the respondent's household.

**NAD** is the number of adults in the respondent's household.

**POSTSTRAT** is the number of people in an age-by-gender or age-by-race-by-gender category in the population of a region or a state divided by the sum of the products of the preceding weights for the respondents in that same age-by-gender or age-by-race-by-gender category. It adjusts for non-coverage and non-response and, before 1995, also adjusts for different probabilities of selection by region, where applicable.

## Calculation of CHILDWT

**CHILDWT = STRWT * 1 OVER NPH * CHILDREN * POSTCH**

**CHILDWT** is the final weight assigned to each child.

**STRWT** accounts for differences in the basic probability of selection among strata (subsets of area code/prefix combinations). It is the inverse of the sampling fraction of each stratum. There is almost never a complete correspondence between strata, which are defined by subsets of area code/prefix combinations, and regions, which are defined by the boundaries of government entities.

**1/NPH** is the inverse of the number of residential telephone numbers in the respondent's household.

**CHILDREN** is the number of children (less than 18 years of age) in the respondent's household.

**POSTCH** is the number of children in an age-by-gender or age-by-race-by-gender category in the population of a region or a state divided by the sum of the products of the preceding weights for the children in that same age-by-gender or age-by-race-by-gender category. It adjusts for non-coverage and non-response.

## Calculation of HOUSEWT

**HOUSEWT** is the weight assigned to each household.

**STRWT** accounts for differences in the basic probability of selection among strata (subsets of area code/prefix combinations). It is the inverse of the sampling fraction of each stratum. There is almost never a complete correspondence between strata, which are defined by subsets of area code/prefix combinations, and regions, which are defined by the boundaries of government entities.

**1/NPH** is the inverse of the number of residential telephone numbers in the household.

**POSTHH** is the number of households in the population of a region or a state divided by the sum of the products of the preceding weights for the households in that same category. It adjusts for non-coverage and non-response.

- Page last reviewed: July 11, 2013
- Page last updated: July 11, 2013
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