0704-0624_ssb_sofs-a_7.16.2021

SUPPORTING STATEMENT – PART B
B. COLLECTIONS OF INFORMATION EMPLOYING STATISTICAL METHODS
If the collection of information employs statistical methods, it should be indicated in
Item 17 of OMB Form 83-I, and the following information should be provided in this Supporting
Statement:

1. Description of the Activity
Describe the potential respondent universe and any sampling or other method used
to select respondents. Data on the number of entities covered in the collection should be
provided in tabular form for the universe as a whole and for each of the strata in the proposed
sample. Indicate the expected response rates for the collection as a whole, as well as the actual
response rates achieved during the last collection, if previously conducted.
The population of interest for the 2021 SOFA consists of active duty members who
are below flag rank and in the Army, Navy, Marine Corps, Air Force, or Coast Guard. OPA uses
a sampling tool developed by the Research Triangle Institute (RTI) to determine the sample size
needed to achieve 95% confidence and an associated precision of 5% or less on each reporting
domain. We select a single-stage, non-proportional stratified random sample to ensure
statistically adequate expected number of responses for the reporting categories (i.e., domains).
For SOFA, OPA uses Service, paygrade, gender, family status, and duty location to define the
initial strata. We collapse these strata when there are fewer than 300 individuals in the stratum.
There were 175 final strata in the 2020 SOFA. Attachment A contains a table with the number
of individuals in the population and sample by strata. The expected weighted response rate for
this survey is about 12%, which is the same as the weighted response rate for this survey in 2020.
2. Procedures for the Collection of Information
Describe any of the following if they are used in the collection of information:
a. Statistical methodologies for stratification and sample selection;
As described above, OPA uses a sampling tool developed by the Research Triangle
Institute (RTI) to determine the sample size needed to achieve 95% confidence and an associated
precision of 5% or less on each reporting category domain. We select a single-stage, nonproportional stratified random sample to ensure statistically adequate expected number of
responses for the reporting domains. For SOFA, OPA uses Service, paygrade, gender, family
status, and duty location to define the initial strata. We collapse these strata when there are
fewer than 300 individuals in the stratum. Once OPA determines the stratum-level sample sizes,
a random number is assigned to every member of the population and the population is sorted by
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stratum and random number prior to sampling, which results in a randomly-ordered population
within each stratum. We then select the appropriate number of members from each stratum.
b. Estimation procedures;
OPA weights the eligible respondents in order to make inferences about the entire
population of active duty members. The weighting methodology utilizes standard weighting
processes. First, we assign a base weight to the sampled member based on the reciprocal of the
selection probability. Second, OPA uses 20-30 administrative variables in the XGBoost
application of Generalized Boosted Model (GBM) to predict survey eligibility and completion.
OPA’s accurate and detailed administrative data on both survey respondents and nonrespondents
provides confidence in our survey estimates. We adjust the sampling weights and then all priorstage weights by the inverse of these model-predicted probabilities to adjust for nonresponse.
Finally, we rake these adjusted weights to known population totals to further reduce the variance
and bias of the estimates.
c. Degree of accuracy needed for the Purpose discussed in the justification;
OPA creates variance strata so precision measures can be associated with each
estimate. We produce precision measures for reporting categories using 95% confidence
intervals with the goal of achieving a precision of 5% or less (e.g, 80% (+/- 5%) of Army E1-E4
are satisfied with their job).
d. Unusual problems requiring specialized sampling procedures; and
OPA recognizes the response rates vary for certain domains of interest such as
Service component and paygrade. To account for this, we average the response rates for the
previous three surveys at the stratum level and these response rates are utilized by the sampling
tool to adjust the sample and compute expected sample sizes.
e. Use of periodic or cyclical data collections to reduce respondent burden.
To reduce burden on active duty members, OPA conducts the SOFA survey
annually, whereas in the past it was conducted twice per year.

3. Maximization of Response Rates, Non-response, and Reliability
Discuss methods used to maximize response rates and to deal with instances of nonresponse. Describe any techniques used to ensure the accuracy and reliability of responses is
adequate for intended purposes. Additionally, if the collection is based on sampling, ensure that
the data can be generalized to the universe under study. If not, provide special justification.

2

To maximize response rates, OPA offers the survey via the Web and uses reminder
letters and emails to maximize response rates. To reduce respondent burden, web-based surveys
use “smart skip” technology to ensure respondents only answer questions that are applicable to
them. To deal with instances of nonresponse, OPA adjusts for nonresponse in the weighting
methodology. To ensure the accuracy and reliability of responses, OPA conducts a nonresponse
bias (NRB) analysis every third survey cycle and will conduct one in 2022. Historically OPA
has found little evidence of significant NRB during these studies; however, OPA statisticians
consider the risk of NRB high and consider it likely the largest source of error in OPA surveys.
OPA uses probability sampling and appropriate weighting to ensure the survey data can be
generalized to the universe under study.

4. Tests of Procedures
Describe any tests of procedures or methods to be undertaken. Testing of potential
respondents (9 or fewer) is encouraged as a means of refining proposed collections to reduce
respondent burden, as well as to improve the collection instrument utility. These tests check for
internal consistency and the effectiveness of previous similar collection activities.
Not applicable.
5. Statistical Consultation and Information Analysis
a. Provide names and telephone number of individual(s) consulted on statistical
aspects of the design.
Mr. David McGrath, Branch Chief; Statistical Methods Team, Methods, Analysis,
and Systems Support, Office of People Analytics (OPA); (571) 372-0983.
Ms. Wendy Barboza, Team Lead; Statistical Methods Team, Methods, Analysis,
and Systems Support, Office of People Analytics (OPA); (571) 372-1099.

b. Provide name and organization of person(s) who will actually collect and analyze
the collected information.
The data will be collected by Data Recognition Corporation (DRC), which is OPA’s
operations contractor. Ms. Valerie Waller is the Senior Managing Director at DRC.
The data will be analyzed by OPA analysts. Lindsay Rock, Monica Wiedemann,
and Amy Campbell are the lead operations analysts.

3

Attachment A. SOFA 2001 - Population and Sample Size by Strata

Stratum
All

Stratum Definitions
Total

Population
Size

Sample
Size

1,360,151

125,765

1

001= 001 ARMY_E1-E4_MALE_SING+CHILD_US&T&OT

4,232

963

2

002= 002 ARMY_E1-E4_MALE_SING+CHILD_OVERSEA

331

77

3

003= 003 ARMY_E1-E4_MALE_DUALSVCS_US&T&OT

2,432

283

4

004= 004 ARMY_E1-E4_MALE_DUALSVCS_OVERSEA

330

52

5

005= 005 ARMY_E1-E4_MALE_OTHERFAMIL_US&T&OT

146,510

18,237

6

006= 006 ARMY_E1-E4_MALE_OTHERFAMIL_EUROPE

7,634

1,107

7

007= 007 ARMY_E1-E4_MALE_OTHERFAMIL_ASIAPI

7,530

753

8

008= 008 ARMY_E1-E4_FEMALE_SING+CHILD_AllREGION

1,692

342

9

009= 009 ARMY_E1-E4_FEMALE_DUALSVCS_US&T&OT

3,434

363

10

010= 010 ARMY_E1-E4_FEMALE_DUALSVCS_OVERSEA

394

72

11

011= 011 ARMY_E1-4_FEMALE_OTHERFAMIL_US&T&OT

23,886

2,334

12

012= 012 ARMY_E1-E4_FEMALE_OTHERFAMIL_EUROPE

1,231

160

13

013= 013 ARMY_E1-E4_FEMALE_OTHERFAMIL_ASIAPI

1,654

167

14

014= 014 ARMY_E5-E9_MALE_SING+CHILD_US&T&OT

8,640

958

15

015= 015 ARMY_E5-E9_MALE_SING+CHILD_EUROPE

387

56

16

016= 016 ARMY_E5-E9_MALE_SING+CHILD_ASIAPI

312

34

17

017= 017 ARMY_E5-E9_MALE_DUALSVCS_US&T&OT

5,770

372

18

018= 018 ARMY_E5-E9_MALE_DUALSVCS_OVERSEA

625

56

19

019= 019 ARMY_E5-E9_MALE_OTHERFAMIL_US&T&OT

125,038

7,290

20

020= 020 ARMY_E5-E9_MALE_OTHERFAMIL_EUROPE

8,347

683

21

021= 021 ARMY_E5-E9_MALE_OTHERFAMIL_ASIAPI

5,565

302

22

022= 022 ARMY_E5-E9_FEMALE_SING+CHILD_US&T&OT

4,125

454

23

023= 023 ARMY_E5-E9_FEMALE_SING+CHILD_OVERSEA

365

54

24

024= 024 ARMY_E5-E9_FEMALE_DUALSVCS_US&T&OT

4,915

310

4

25

025= 025 ARMY_E5-E9_FEMALE_DUALSVCS_OVERSEA

526

53

26

026= 026 ARMY_E5-9_FEMALE_OTHERFAMIL_US&T&OT

12,370

719

27

027= 027 ARMY_E5-E9_FEMALE_OTHERFAMIL_EUROPE

989

92

28

028= 028 ARMY_E5-E9_FEMALE_OTHERFAMIL_ASIAPI

729

47

29

029= 029 ARMY_W1-W5_MALE_SING+CHILD_AllREGION

776

162

30

030= 030 ARMY_W1-W5_MALE_DUALSVCS_AllREGION

395

78

31

031= 031 ARMY_W1-W5_MALE_OTHERFAMIL_US&T&OT

10,280

1,755

32

032= 032 ARMY_W1-W5_MALE_OTHERFAMIL_EUROPE

671

112

33

033= 033 ARMY_W1-W5_MALE_OTHERFAMIL_ASIAPI

696

114

34

034= 034 ARMY_W1-W5_FEMALE_NotOther_AllREGION

566

119

35

035= 035 ARMY_W1-W5_FEMALE_OTHERFAMIL_AllREGION

867

158

36

036= 036 ARMY_O1-O3_MALE_SING+CHILD_AllREGION

816

81

37

037= 037 ARMY_O1-O3_MALE_DUALSVCS_AllREGION

1,398

92

38

038= 038 ARMY_O1-O3_MALE_OTHERFAMIL_US&T&OT

33,899

1,916

39

039= 039 ARMY_O1-O3_MALE_OTHERFAMIL_EUROPE

1,751

115

40

040= 040 ARMY_O1-O3_MALE_OTHERFAMIL_ASIAPI

1,216

67

41

041= 041 ARMY_O1-O3_FEMALE_SING+CHILD_AllREGION

472

45

42

042= 042 ARMY_O1-O3_FEMALE_DUALSVCS_AllREGION

1,762

115

43

043= 043 ARMY_O1-O3_FEMALE_OTHERFAMIL_US&T&OT

7,308

428

44

044= 044 ARMY_O1-O3_FEMALE_OTHERFAMIL_EUROPE

392

33

45

045= 045 ARMY_O1-O3_FEMALE_OTHERFAMIL_ASIAPI

311

20

46

046= 046 ARMY_O4-O6_MALE_SING+CHILD_AllREGION

844

79

47

047= 047 ARMY_O4-O6_MALE_DUALSVCS_AllREGION

987

68

48

048= 048 ARMY_O4-O6_MALE_OTHERFAMIL_US&T&OT

19,537

1,206

49

049= 049 ARMY_O4-O6_MALE_OTHERFAMIL_EUROPE

1,707

120

50

050= 050 ARMY_O4-O6_MALE_OTHERFAMIL_ASIAPI

950

62

51

051= 051 ARMY_O4-O6_FEMALE_SING+CHILD_AllREGION

509

50

5

52

052= 052 ARMY_O4-O6_FEMALE_DUALSVCS_AllREGION

1,002

69

53

053= 053 ARMY_O4-O6_FEMALE_OTHERFAMIL_US&T&OT

3,201

197

54

054= 054 ARMY_O4-O6_FEMALE_OTHERFAMIL_OVERSEA

373

31

55

055= 055 NAVY_E1-E4_MALE_SING+CHILD_AllREGION

578

115

56

056= 056 NAVY_E1-E4_MALE_DUALSVCS_AllREGION

2,829

344

57

057= 057 NAVY_E1-E4_MALE_OTHERFAMIL_US&T&OT

82,795

10,088

58

058= 058 NAVY_E1-E4_MALE_OTHERFAMIL_EUROPE

1,225

193

59

059= 059 NAVY_E1-E4_MALE_OTHERFAMIL_ASIAPI

5,825

620

60

060= 060 NAVY_E1-E4_FEMALE_SING+CHILD_AllREGION

1,045

196

61

061= 061 NAVY_E1-E4_FEMALE_DUALSVCS_AllREGION

3,813

452

62

062= 062 NAVY_E1-E4_FEMALE_OTHERFAMIL_US&T&OT

22,687

2,615

63

063= 063 NAVY_E1-E4_FEMALE_OTHERFAMIL_EUROPE

479

73

64

064= 064 NAVY_E1-E4_FEMALE_OTHERFAMIL_ASIAPI

1,740

186

65

065= 065 NAVY_E5-E9_MALE_SING+CHILD_US&T&OT

5,363

566

66

066= 066 NAVY_E5-E9_MALE_SING+CHILD_OVERSEA

331

43

67

067= 067 NAVY_E5-E9_MALE_DUALSVCS_AllREGION

5,597

347

68

068= 068 NAVY_E5-E9_MALE_OTHERFAMIL_US&T&OT

107,142

5,982

69

069= 069 NAVY_E5-E9_MALE_OTHERFAMIL_EUROPE

2,817

219

70

070= 070 NAVY_E5-E9_MALE_OTHERFAMIL_ASIAPI

7,743

440

71

071= 071 NAVY_E5-E9_FEMALE_SING+CHILD_AllREGION

3,791

396

72

072= 072 NAVY_E5-E9_FEMALE_DUALSVCS_AllREGION

5,320

322

73

073= 073 NAVY_E5-E9_FEMALE_OTHERFAMIL_US&T&OT

16,449

942

74

074= 074 NAVY_E5-E9_FEMALE_OTHERFAMIL_EUROPE

550

49

75

075= 075 NAVY_E5-E9_FEMALE_OTHERFAMIL_ASIAPI

1,027

64

76

076= 076 NAVY_W1-W5_ALLGEN_AllFamily_AllREGION

1,911

331

77

077= 077 NAVY_O1-O3_MALE_SING+CHILD_AllREGION

412

42

78

078= 078 NAVY_O1-O3_MALE_DUALSVCS_AllREGION

971

84

6

79

079= 079 NAVY_O1-O3_MALE_OTHERFAMIL_US&T&OT

23,191

1,726

80

080= 080 NAVY_O1-O3_MALE_OTHERFAMIL_EUROPE

417

37

81

081= 081 NAVY_O1-O3_MALE_OTHERFAMIL_ASIAPI

1,249

92

82

082= 082 NAVY_O1-O3_FEMALE_NotOther_AllREGION

1,579

139

83

083= 083 NAVY_O1-O3_FEMALE_OTHERFAMIL_US&T&OT

5,634

433

84

084= 084 NAVY_O1-O3_FEMALE_OTHERFAMIL_OVERSEA

544

49

85

085= 085 NAVY_O4-O6_MALE_SING+CHILD_AllREGION

439

51

86

086= 086 NAVY_O4-O6_MALE_DUALSVCS_AllREGION

584

55

87

087= 087 NAVY_O4-O6_MALE_OTHERFAMIL_US&T&OT

14,289

1,150

88

088= 088 NAVY_O4-O6_MALE_OTHERFAMIL_EUROPE

707

70

89

089= 089 NAVY_O4-O6_MALE_OTHERFAMIL_ASIAPI

859

70

90

090= 090 NAVY_O4-O6_FEMALE_NotOther_AllREGION

876

87

91

091= 091 NAVY_O4-O6_FEMALE_OTHERFAMIL_AllREGION

2,369

202

92

092= 092 USMC_E1-E4_MALE_SING+CHILD_AllREGION

365

103

93

093= 093 USMC_E1-E4_MALE_DUALSVCS_AllREGION

1,837

268

94

094= 094 USMC_E1-E4_MALE_OTHERFAMIL_US&T&OT

82,174

15,860

95

095= 095 USMC_E1-E4_MALE_OTHERFAMIL_EUROPE

1,123

204

96

096= 096 USMC_E1-E4_MALE_OTHERFAMIL_ASIAPI

12,063

1,441

97

097= 097 USMC_E1-E4_FEMALE_NotOther_AllREGION

2,032

268

98

098= 098 USMC_E1-E4_FEMALE_OTHERFAMIL_US&T&OT

6,804

1,004

99

099= 099 USMC_E1-E4_FEMALE_OTHERFAMIL_OVERSEA

1,190

114

100

100= 100 USMC_E5-E9_MALE_SING+CHILD_AllREGION

2,074

249

101

101= 101 USMC_E5-E9_MALE_DUALSVCS_AllREGION

1,846

178

102

102= 102 USMC_E5-E9_MALE_OTHERFAMIL_US&T&OT

39,232

3,524

103

103= 103 USMC_E5-E9_MALE_OTHERFAMIL_EUROPE

663

75

104

104= 104 USMC_E5-E9_MALE_OTHERFAMIL_ASIAPI

4,832

343

105

105= 105 USMC_E5-E9_FEMALE_SING+CHILD_AllREGION

653

84

7

106

106= 106 USMC_E5-E9_FEMALE_DUALSVCS_AllREGION

1,275

119

107

107= 107 USMC_E5-E9_FEMALE_OTHERFAMIL_US&T&OT

2,320

221

108

108= 108 USMC_E5-E9_FEMALE_OTHERFAMIL_OVERSEA

303

30

109

109= 109 USMC_W1-W5_ALLGEN_AllFamily_US&T&OT

1,896

316

110

110= 110 USMC_W1-W5_ALLGEN_AllFamily_OVERSEA

346

48

111

111= 111 USMC_O1-O3_MALE_NotOther_AllREGION

496

121

112

112= 112 USMC_O1-O3_MALE_OTHERFAMIL_US&T&OT

9,953

2,217

113

113= 113 USMC_O1-O3_MALE_OTHERFAMIL_OVERSEA

1,209

230

114

114= 114 USMC_O1-O3_FEMALE_AllFamily_AllREGION

1,342

298

115

115= 115 USMC_O4-O6_MALE_NotOther_AllREGION

361

117

116

116= 116 USMC_O4-O6_MALE_OTHERFAMIL_US&T&OT

5,130

1,533

117

117= 117 USMC_O4-O6_MALE_OTHERFAMIL_OVERSEA

718

211

118

118= 118 USMC_O4-O6_FEMALE_AllFamily_AllREGION

401

121

119

119= 119 USAF_E1-E4_MALE_SING+CHILD_AllREGION

1,122

149

120

120= 120 USAF_E1-E4_MALE_DUALSVCS_US&T&OT

3,401

231

121

121= 121 USAF_E1-E4_MALE_DUALSVCS_OVERSEA

550

57

122

122= 122 USAF_E1-E4_MALE_OTHERFAMIL_US&T&OT

81,060

4,589

123

123= 123 USAF_E1-E4_MALE_OTHERFAMIL_EUROPE

4,713

370

124

124= 124 USAF_E1-E4_MALE_OTHERFAMIL_ASIAPI

6,020

292

125

125= 125 USAF_E1-E4_FEMALE_SING+CHILD_AllREGION

1,094

128

126

126= 126 USAF_E1-E4_FEMALE_DUALSVCS_US&T&OT

4,521

253

127

127= 127 USAF_E1-E4_FEMALE_DUALSVCS_EUROPE

329

38

128

128= 128 USAF_E1-E4_FEMALE_DUALSVCS_ASIAPI

339

30

129

129= 129 USAF_E1-E4_FEMALE_OTHERFAMIL_US&T&OT

20,124

1,059

130

130= 130 USAF_E1-E4_FEMALE_OTHERFAMIL_EUROPE

1,264

103

131

131= 131 USAF_E1-E4_FEMALE_OTHERFAMIL_ASIAPI

1,064

56

132

132= 132 USAF_E5-E9_MALE_SING+CHILD_US&T&OT

4,531

340

8

133

133= 133 USAF_E5-E9_MALE_SING+CHILD_OVERSEA

578

48

134

134= 134 USAF_E5-E9_MALE_DUALSVCS_US&T&OT

9,178

402

135

135= 135 USAF_E5-E9_MALE_DUALSVCS_EUROPE

751

51

136

136= 136 USAF_E5-E9_MALE_DUALSVCS_ASIAPI

671

30

137

137= 137 USAF_E5-E9_MALE_OTHERFAMIL_US&T&OT

81,104

3,256

138

138= 138 USAF_E5-E9_MALE_OTHERFAMIL_EUROPE

7,868

439

139

139= 139 USAF_E5-E9_MALE_OTHERFAMIL_ASIAPI

8,042

300

140

140= 140 USAF_E5-E9_FEMALE_SING+CHILD_US&T&OT

3,040

230

141

141= 141 USAF_E5-E9_FEMALE_SING+CHILD_OVERSEA

334

29

142

142= 142 USAF_E5-E9_FEMALE_DUALSVCS_US&T&OT

7,723

322

143

143= 143 USAF_E5-E9_FEMALE_DUALSVCS_EUROPE

645

41

144

144= 144 USAF_E5-E9_FEMALE_DUALSVCS_ASIAPI

519

25

145

145= 145 USAF_E5-E9_FEMALE_OTHERFAMIL_US&T&OT

11,884

483

146

146= 146 USAF_E5-E9_FEMALE_OTHERFAMIL_EUROPE

1,125

66

147

147= 147 USAF_E5-E9_FEMALE_OTHERFAMIL_ASIAPI

892

37

148

148= 148 USAF_O1-O3_MALE_NotOther_AllREGION

2,240

130

149

149= 149 USAF_O1-O3_MALE_OTHERFAMIL_US&T&OT

23,670

1,182

150

150= 150 USAF_O1-O3_MALE_OTHERFAMIL_EUROPE

775

47

151

151= 151 USAF_O1-O3_MALE_OTHERFAMIL_ASIAPI

909

42

152

152= 152 USAF_O1-O3_FEMALE_NotOther_AllREGION

2,485

133

153

153= 153 USAF_O1-O3_FEMALE_OTHERFAMIL_US&T&OT

6,033

291

154

154= 154 USAF_O1-O3_FEMALE_OTHERFAMIL_OVERSEA

566

31

155

155= 155 USAF_O4-O6_MALE_SING+CHILD_AllREGION

500

41

156

156= 156 USAF_O4-O6_MALE_DUALSVCS_AllREGION

1,637

88

157

157= 157 USAF_O4-O6_MALE_OTHERFAMIL_US&T&OT

18,401

1,017

158

158= 158 USAF_O4-O6_MALE_OTHERFAMIL_EUROPE

1,281

82

159

159= 159 USAF_O4-O6_MALE_OTHERFAMIL_ASIAPI

753

37

9

160

160= 160 USAF_O4-O6_FEMALE_SING+CHILD_AllREGION

356

26

161

161= 161 USAF_O4-O6_FEMALE_DUALSVCS_AllREGION

1,243

66

162

162= 162 USAF_O4-O6_FEMALE_OTHERFAMIL_US&T&OT

3,230

185

163

163= 163 USAF_O4-O6_FEMALE_OTHERFAMIL_OVERSEA

393

22

164

164= 164 USCG_E1-E4_MALE_AllFamily_US&T&OT

10,653

2,543

165

165= 165 USCG_E1-E4_FEMALE_AllFamily_US&T&OT

1,815

345

166

166= 166 USCG_E5-E9_MALE_SING+CHILD_US&T&OT

774

59

167

167= 167 USCG_E5-E9_MALE_DUALSVCS_US&T&OT

527

39

168

168= 168 USCG_E5-E9_MALE_OTHERFAMIL_AllREGION

15,475

1,076

169

169= 169 USCG_E5-E9_FEMALE_NotOther_US&T&OT

692

49

170

170= 170 USCG_E5-E9_FEMALE_OTHERFAMIL_NOTEUR

1,884

130

171

171= 171 USCG_W1-W5_ALLGEN_AllFamily_AllREGION

1,783

107

172

172= 172 USCG_O1-O3_MALE_AllFamily_AllREGION

3,162

1,139

173

173= 173 USCG_O1-O3_FEMALE_AllFamily_NOTASIA

1,193

415

174

174= 174 USCG_O4-O6_MALE_AllFamily_AllREGION

2,207

933

175

175= 175 USCG_O4-O6_FEMALE_AllFamily_AllREGION

534

207

10