2020 NSCH Table of State Sample Sizes

Appendix C

2020 National Survey of Children’s Health
Table of State Sample Sizes

2020 NSCH - Estimated State Sample Sizes

Base Sample
Oversampling
Rate 1
'k'
State Sample Sizes
Alabama
4
Alaska
3
Arizona
3
Arkansas
3
California
3
Colorado
3
Connecticut
3
Delaware
3
District of Columbia
6
Florida
3
Georgia
3
Hawaii
3
Idaho
3
Illinois
3
Indiana
3
Iowa
6
Kansas
4
Kentucky
4
Louisiana
3
Maine
7
Maryland
3
Massachusetts
4
Michigan
4
Minnesota
4
Mississippi
4
Missouri
4
Montana
5
Nebraska
5
Nevada
3
New Hampshire
5
New Jersey
3
New Mexico
4
New York
3
North Carolina
4
North Dakota
6
Ohio
4
Oklahoma
4
Oregon
4
Pennsylvania
4
Rhode Island
4
South Carolina
4
South Dakota
5
Tennessee
4
Texas
3
Utah
3
Vermont
5
Virginia
3
Washington
3
West Virginia
4
Wisconsin
4
Wyoming
4
Total
Proportion by Strata

Proportion of
Households with
Children from
2018 ACS
'P'
29%
27%
32%
32%
44%
37%
39%
37%
24%
32%
37%
32%
35%
36%
38%
26%
36%
29%
32%
22%
40%
36%
36%
39%
29%
34%
21%
28%
35%
30%
42%
22%
34%
35%
23%
37%
27%
34%
35%
33%
31%
24%
34%
40%
48%
24%
40%
37%
23%
36%
27%

Base
Sample
Sampling
Variance1
‘R’
1.03
0.98
0.98
0.98
1.03
0.98
0.99
0.98
1.06
0.98
1.01
1.06
0.98
0.98
0.99
1.05
1.06
1.00
1.00
1.05
0.99
1.04
1.04
1.02
1.05
1.05
0.99
1.02
0.99
1.06
1.01
1.01
0.99
1.06
1.01
1.05
1.04
1.03
1.02
1.05
1.04
1.01
1.06
1.03
1.03
0.99
0.98
0.98
0.99
1.03
0.99

Total
Sample 2
4900
6900
5100
5900
4100
9400
3800
4600
4400
5200
5300
4800
3400
4000
3900
3100
3300
4600
6400
3900
3500
3200
3100
2400
6000
3900
5100
5200
4800
3700
3600
6300
4900
3900
3800
3500
5300
14500
3500
4000
4900
4100
3900
4800
2700
4000
3300
3700
5500
6900
5100
240,000

Stratum 1
Stratum 2a
Sample
Sample
(Admin Flag
(Admin Flag
for HHLD
for HHLD w/o
w/Children)
Children)
3000
1900
3000
3900
2800
2200
3200
2700
2800
1300
5200
4200
2400
1400
2900
1700
2900
1400
3100
2100
3300
2000
2000
2800
2000
1400
2500
1600
2400
1400
2000
1100
2200
1100
2700
1900
3700
2700
2400
1500
2300
1200
2100
1100
2100
1000
1600
750
3600
2400
2500
1300
2600
2500
3300
1900
2900
1900
2400
1300
2300
1300
3100
3200
2800
2100
2600
1400
2300
1500
2400
1100
2900
2400
9500
5100
2300
1200
2600
1500
3100
1800
2300
1800
2600
1300
3000
1700
1900
800
2300
1700
2100
1200
2200
1500
2600
2900
4600
2300
2700
2400
144,000
96,000
60%
40%

1 These are the Stratum 1 oversampling rates and the sampling variances for the base production sample only. Colorado, Nebraska,
Oregon, and Wisconsin all have additional sample that may have different oversampling rates and sampling variances.
2 Sample sizes include both the base production sample as well as the additional sample in CO, NE, OR, and WI. All sample sizes
have been rounded.

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Calculations for State Sample Sizes
The oversampling rate (k) was calculated to maximize the sample from Stratum 1 without increasing the variance (R)
too much beyond that of a proportional stratified design of a similar cost.
(P) is the proportion of households with children based on the 2018 ACS audit 1.
The portion of the sample coming from each stratum was calculated using the oversampling rate (k) and the proportion
of all households in each of the sampling strata (W1 and W2a). Address valid rates, child prevalence rates, and Screener
and Topical returns rates were estimated by state and stratum primarily using previous years’ response outcomes. A
national total sample size of approximately 240,000 was determined based on budget. This includes the base production
sample for all states as well as additional sample in Colorado, Nebraska, Oregon, and Wiscon. We expect the base
production sample will produce approximately 700 Topical interviews per state. The expected number of interviews
along with previous years’ response information was used to calculate stratum sample sizes (n1 and n2a) in each state.
For example, in Alabama 2:
The oversampling rate (k) was recalculated to be 4.0, for an R = 1.03. Of the 2018 ACS households eligible for NSCH
sampling, 28.1% would be put in Stratum 1 (W1) and 71.9% would be put in Stratum 2a (W2a).
The portion of the sample coming from Stratum 1 was estimated to be (k*W1) / (W2a + k*W1) = 61.0% and the
portion of the sample from Stratum 2a was 39.0%.
We can expect a completed Topical from 91.5% (Valid) * 39.5% (Screener) * 79.6% (Children) * 75.5% (Topical) =
21.7% of addresses in Stratum 1 and 75.7% (Valid) * 43.1% (Screener) * 9.0% (Children) * 82.4% (Topical) = 2.4% of
addresses in Stratum 2a.
Since we expect to get 700 Topicals per state, we can get the state sample size (n) by evaluating the following:
(n * Portion of the sample from Stratum 1 * Stratum 1 completed Topical rate) + (n * Portion of the sample from
Stratum 2a * Stratum 2a completed Topical rate) = 700.
Within rounding, it then follows that n = 700 / (61.0% * 21.7% + 39.0% * 2.4%) = 4900. Now n1 = 4900
* 61.0% = 3000 and n2a = 4900 * 39.0% = 1900.

1

Before mailout, this will be updated with the 2019 ACS.

2

Note that numbers have been rounded here for all calculations.

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