Age-adjusted Rates on IBIS Query System (Directly Age-adjusted)

Age Adjustment Weights (Updated January, 2012)

The age-specific rates for each age group in the study population are multiplied by the proportion of people in the same age group in the standard population distribution. The sum of these products is the age-adjusted, or age-standardized rate. The age-adjusted rate can be considered an average of each of the individual age-specific rates, but rather than being a simple average, it is a weighted average with each age-specific rate weighted by the proportion of people in that age group in the U.S. 2000 standard population.

Age-adjusted rates control for age effects, allowing better comparability of rates across areas. Age-adjustment may also be used to control for age effects when comparing across several years of data, as the age distribution of the population changes over time. Only rates adjusted to the same standard population can be compared. Age adjustment is not appropriate if the age-specific death rates in the population of interest do not have a consistent relationship. The age-adjusted rate is hypothetical, and is useful only for comparing populations, either over time, by geographic area, by sex, or by racial/ethnic subgroups. For more information, see "Health Event Counts and Crude, Age-specific, and Age-adjusted Rates" Help

The IBIS query system uses the U.S. 2000 standard population weights for all age-adjusted measures.

For more information on age adjustment using the 2000 projected U.S. population, see http://www.cdc.gov/nchs/data/statnt/statnt20.pdf

All weights used on IBIS are from the master list of 2000 U.S. projected and age-adjustedment weights.

U.S. 2000 Standard Population 11 Age Groups Weights (Used by Mortality, Hospital Discharge, ED Encounter, ED Primary Care Sensitive Conditions and UHAS* IBIS Query Modules)

	Age Group	U.S. 2000 Population Projection (in thousands)	Weight
1	Under 1 Year	3,795	0.013818
2	1 - 4 Years	15,192	0.055317
3	5 - 14 Years	39,977	0.145565
4	15 - 24 Years	38,077	0.138646
5	25 - 34 Years	37,233	0.135573
6	35 - 44 Years	44,659	0.162613
7	45 - 54 Years	37,030	0.134834
8	55 - 64 Years	23,961	0.087247
9	65 - 74 Years	18,136	0.066037
10	75 - 84 Years	12,315	0.044842
11	85 Years and Over	4,259	0.015508
	Total, All ages	274,634	1

Weight=Age-specific Population/Total population in All Age groups

*UHAS normalizes the weights when (1) age restriction has applied to the survey questions. (2) certain age groups have no observations.

U.S. 2000 Standard Population 10 Age Groups Weights (Used by Cancer Registry IBIS Query Modules)

	Age Group	U.S. 2000 Population Projection (in thousands, from #1)	Weight
1	0 - 4 Years	18,987	0.069135
2	5 - 14 Years	39,977	0.145565
3	15 - 24 Years	38,077	0.138646
4	25 - 34 Years	37,233	0.135573
5	35 - 44 Years	44,659	0.162613
6	45 - 54 Years	37,030	0.134834
7	55 - 64 Years	23,961	0.087247
8	65 - 74 Years	18,136	0.066037
9	75 - 84 Years	12,315	0.044842
10	85 Years and Over	4,259	0.015508
	Total, All ages	274,634	1

Weight=Age-specific Population/Total population in All Age groups

U.S. 2000 Standard Population 8 Age Groups Weights (Used by BRFSS* IBIS Query Modules)

	Age Group	U.S. 2000 Population Projection (in thousands)	Weight
1	18 - 24 Years	26,258	0.1288
2	25 - 34 Years	37,233	0.1827
3	35 - 44 Years	44,659	0.2191
4	45 - 54 Years	37,030	0.1817
5	55 - 64 Years	23,961	0.1175
6	65 - 74 Years	18,136	0.0889
7	75 - 84 Years	12,315	0.0604
8	85 Years and Over	4,259	0.0209
	Total, 18 years and older	203,851	1

Weight=Age-specific Population/Total population in All Age groups

*BRFSS normalizes the weights when certain age groups have no observations.

U.S. 2000 Standard Population 3 Age Groups Weights (Used by BRFSS IBIS Query Modules Including Race)

	Age Group	U.S. 2000 Population Projection (in thousands)	Weight
1	18 - 34 Years	63,491	0.3115
2	35 - 49 Years	64,465	0.3162
3	50+ Years	75,895	0.3723
	Total	203,851	1

Weight=Age-specific Population/Total population in All Age groups

*BRFSS normalizes the weights when certain age groups have no observations.

U.S. 2000 Standard Population 3 Age Groups Weights (Used by Mortality IBIS Query Modules Including Race)

	Age Group	U.S. 2000 Population Projection (in thousands)	Weight
1	0 - 44 Years	178,933	0.651532
2	45 - 65 Years	60,991	0.22.2081
3	65+ Years	30,710	0.126387
	Total, All ages	274,634	1

Weight=Age-specific Population/Total population in All Age groups

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