Appendix B

NSCH_OMB_AppendixB.docx

National Survey of Children's Health

Appendix B

OMB: 0607-0990

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Appendix B


State Sample Sizes


State Sample Sizes

Oversample Ratio
'k'

Proportion of
Households with
Children from
2015 ACS
'P'




Sampling Variance

R’

Total
Sample

Stratum 1
Sample
(Admin Flag
for HHLD
w/Children)

Stratum 2a
Sample
(Admin Flag
for HHLD
w/o Children)

Alabama

3.0

38%

0.99

4144

2460

1684

Alaska

3.0

31%

1.04

4196

1809

2387

Arizona

3.0

42%

1.03

3256

2018

1238

Arkansas

3.0

37%

1.00

3961

2190

1771

California

3.0

50%

1.03

2896

2060

836

Colorado

3.0

46%

1.00

2478

1658

820

Connecticut

3.0

45%

1.00

2700

1841

859

Delaware

3.0

50%

1.01

2791

2088

703

District of Columbia

5.0

32%

1.08

3195

2273

922

Florida

3.0

39%

0.99

3812

2494

1317

Georgia

3.0

44%

1.02

3609

2449

1160

Hawaii

2.0

36%

0.99

3457

1293

2164

Idaho

3.0

43%

1.01

2580

1688

892

Illinois

3.0

45%

1.01

2706

1815

891

Indiana

3.0

47%

1.02

2849

2005

844

Iowa

3.0

49%

0.99

2283

1646

638

Kansas

3.0

47%

1.00

2794

1947

848

Kentucky

3.0

41%

1.01

3287

2064

1223

Louisiana

3.0

38%

1.00

4650

2998

1652

Maine

5.0

28%

1.02

3257

1856

1401

Maryland

4.0

49%

1.09

2369

1850

519

Massachusetts

3.0

45%

0.99

2422

1659

764

Michigan

4.0

46%

1.06

2368

1789

578

Minnesota

3.0

53%

1.00

1873

1409

464

Mississippi

3.0

38%

1.02

4959

3003

1956

Missouri

3.0

43%

1.01

2923

1897

1026

Montana

4.0

31%

1.06

3168

1718

1450

Nebraska

3.0

48%

0.99

2393

1681

713

Nevada

3.0

41%

1.01

3848

2532

1316

New Hampshire

4.0

39%

1.01

2646

1820

827

New Jersey

3.0

47%

1.02

2689

1847

842

New Mexico

3.0

33%

1.02

4188

2063

2125

New York

3.0

39%

1.01

3262

1985

1277

North Carolina

4.0

40%

1.06

2962

2076

886

North Dakota

4.0

39%

1.07

2649

1720

929

Ohio

4.0

46%

1.07

2577

1933

644

Oklahoma

3.0

37%

1.03

4253

2416

1837

Oregon

4.0

44%

1.06

2319

1655

664

Pennsylvania

4.0

43%

1.05

2416

1755

661

Rhode Island

4.0

40%

1.05

3024

2138

886

South Carolina

4.0

40%

1.07

3310

2338

972

South Dakota

3.0

43%

1.02

2550

1609

940

Tennessee

4.0

42%

1.07

2980

2182

798

Texas

3.0

47%

1.05

3347

2316

1030

Utah

3.0

56%

1.05

2076

1573

503

Vermont

4.0

30%

0.99

2858

1504

1354

Virginia

3.0

48%

0.99

2375

1719

656

Washington

3.0

47%

1.01

2368

1629

739

West Virginia

3.0

32%

1.02

4047

1881

2166

Wisconsin

3.0

50%

0.99

2012

1466

545

Wyoming

3.0

34%

1.01

3923

1920

2003

Total




156,054

99,733

56,321

Proportion by Strata





64%

36%


Calculations for State Sample Sizes

The oversampling factor (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 2015 ACS audit.

The portion of the sample coming from each stratum was calculated using the oversample rate (k) and the portion of all households in each stratum (W1 and W2). These estimates were then used with the prevalence of households with children in each stratum (P1 and P2) to get the percent of the sample expected to have children. Address valid rates, Screener and Topical returns rates were estimated by state (and address valid rates by Stratum as well) using 2016 response outcomes. Using this response information, along with the percent of the sample expected to have children in each state, we calculated the sample size needed to get 460 topical interviews in each state.


For example, in Alabama:

The oversampling rate (k) was recalculated to be 3.0, for an R = .99.

Using the ACS x NSCH Flag tabulations:



NSCH Administrative Flag for Household with Children

NSCH Administrative Flag for Household without Children

Proportion of All Households with children from 2014 ACS

2015 ACS Household with Children

74.5% (P1)

15.8% (P2)

22.4% (W1)

2015 ACS Household without Children

25.5%

84.2%

77.6% (W2)


The portion of the sample coming from Stratum 1 was estimated to be (k*W1)/(W2 + k*W1) = 64.1% and the portion of the sample from Stratum 2a was 35.9%.

Within our sample we expect 74.5%*64.1% + 15.8%*35.9% = 53.4% to have children.


We can expect a completed interview from 84.4% (Valid) * 36.9% (Screener) * 53.4% (Children) * 66.7% (Topical) = 11.1% of addresses.


Now we take the target of 460 interviews and adjust for the expected response and the percent of the sample with children to get the state sample size: 460*(11.1%)-1 = 4144.

Now n1 = 64.1%*4144=2460 and n2 = 35.9%*4144 = 1684.




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