Sample Selection: SAFE Project

Study Design• 3-Level Multi Site Cluster Randomized Trial (CRT) with

power=0.80; alpha=0.05; and r=0.01

• 3 arms with different combinations of intervention, to be measured at baseline and endline in 18 months apart

Arm 1 Arm 2 Arm 3

• Clinic • Clinic • Clinic

• Community campaigning

• Community campaigning

• Community campaigning

• Female groups • Female groups

• Male groups

Why 3 arms?• A comparison between

Arms 1 and 2 will inform the added advantage of male groups on top of clinic, community campaigning and female groups

• A comparison between Arms 3 and 2 will inform the added advantage of female groups on top of clinic and community campaigning

Arm 1 Arm 2

• Clinic • Clinic

• Community campaigning

• Community campaigning

• Female groups • Female groups

• Male groups

Arm 2 Arm 3

• Clinic • Clinic

• Community campaigning

• Community campaigning

• Female groups

All common intervention components across arms, i.e.,

clinic, community campaigning and female group sessions

must be similar across arms of all sitesfor ensuring comparability

Standardization of intervention components

Study Subjects and Sample SizeAge group and sex

Marital status

Effect variable

MDES Clusters for 3 arms

Cluster size (N)

Cluster size (N) with 20%

over-sampling

No. of sites (K)

Sample-3 arms

15-19 females

Married; Unmarried

Marriage 45% 51 15 18 3 2754

20-29 females

Married; Unmarried

Violence exposure 55% 27 15

183 1458

18-35 males

Married; Unmarried

SRHR Knowledge

and attitudes

55% 27 1518

3 1458

Total Female sample (2754+1458) 4212

Total Male sample  1458

Total sample (2754+1458+1458) 5670

Process of sample selection• First, identify the three study sites, each with one MS clinic

• All sites should have similar type of MS clinics (for instance, 3 UPHCP referral clinics have been selected for the project)

• Each site needs to have at least 51 clusters of young females (YF) and 27 clusters of adult females (AF)

• Adult female clusters can be merged with YF clusters if each cluster has at least 18 x 2= 36 households; because only one respondent (YF/AF) will be interviewed from each selected household (Caution: This rule does not apply for conducting group sessions)

• Thus, each cluster need to have minimum 36 hhs, preferably 50 hhs to avoid refusal/drop out

Continued….

Process of sample selection• Males cannot be interviewed from the same cluster as that of

the females for the safety of the females

• Therefore, additional 27 clusters need to be selected from each site

• Thus, each site requires a total 78 (Female: 51 + Male: 27) non-contaminated clusters

• 78 clusters will be randomly assigned to the three arms, with 26 clusters for each arm

How to form a cluster• Cluster, preferably, should have geographical

boundary• Cluster, preferably should have

natural/administrative characteristics binding them into a group; for instance, a village or a para can be a cluster, which however, is difficult to achieve in a slum setting

• Clusters need to be identified and marked during enumeration/listing

• Either natural factors or houses should be identified as buffer zone between clusters to control contamination

Understanding the temporary settlement/slum setting

Three study sites include 3 UPHCP referral clinics-

• Mohammadpur Landmark: Sikder Medical, PoolparNo. of slums-8 ; Population-30,285

• BashaboLandmark: Buddha MandirNo. of slums-7; Population-14,200 (MS will identify more slum population)

• MohakhaliLandmark: Mohakhali FlyoverNo. of slums-5; Population-30,500

Understanding the temporary settlement/slum setting

Three study sites include 3 UPHCP referral clinics-

• Mohammadpur Landmark: Sikder Medical, PoolparNo. of slums-8 ; Population-30,285

• BashaboLandmark: Buddha MandirNo. of slums-7; Population-14,200 (MS will identify more slum population)

• MohakhaliLandmark: Mohakhali FlyoverNo. of slums-5; Population-30,500

Minimum population requirement per site

Each site must have 25,000-30,000 population(5,000 to 6,000 households) because---

•78 clusters x 50 households= 3,900 HHs•3,900 HHs x 5 members = 19,500 population•Additional 2,000 HHs with 10,000 population are needed for creating buffer zone among clusters

Note: 19,500 population is enough to have 918 young females of 15-19 years [19500 x 10% 15-19 years old x 50% female]

Each of the three site has 1 clinic and 5 to 8 slums

Mohammadpur clinic [Poolpar]

Bashabo clinic [Mandir]

Mohakhali clinic [Flyover]

Site-1 Site-2 Site-3

Slum 1

Slum 2

Slum 3

Slum 4

Slum 5

Identification of clusters across 3 armsMohakhali Clinic

Arm 1

Arm 2

Arm 3

Re-randomization

• Background characteristics, especially proportion of married girls and level of education should be similar across 3 arms of each site

• Since ICDDR,B will enter data of the listing, after randomly assigning the clusters and looking into the differences in terms of marital status of young females, arms may be reassigned through rerandomization

Scopes for contamination

• Contamination by participation- females subjects from arm 3 may take part in or recruited into female groups of arms 1 or 2; similarly male subjects from arms 2 and 3 may take part in male groups of arm 2

• Contamination by diffusion- geographically proximate clusters with people having regular and meaningful social interaction may contaminate by diffusion

Measures to reduce contamination• Contamination by participation

– Each hh will be marked with hh and cluster numbers; – Frontline staff will be cautioned and supervised so

that they do not recruit subjects from inappropriate arms (for example, females from arm 3; and males from arms 2 and 3)

• Contamination by diffusion– geographical and buffer hhs will be identified; – social groups centering on leaders’

houses/landmarks/shops will be identified and kept in the same cluster to reduce the diffusion through social networking

Clusters for survey and groups for intervention per site across 3 arms

Mohakhali ClinicArm 1

Arm 2

Arm 380 FGs (50 YF + 30 AF)

44 MGs (50 YF + 30 AF)

26 FCs (17 YF + 9AF)

9 MCs

80 FGs (50 YF + 30 AF)

26 FCs (17 YF + 9AF)

9 MCs

26 FCs (17 YF + 9AF)

9 MCs

Number of female and male groupsGroup characteristics

Arm 1 Arm 2 Arm 3 Total groups in each site

Total groups in 3 sites

• 10-14 female groups 16 16 - 32 96

• 15-19 female groups 50 50 - 100 300

• 20-29 female groups 30 30 - 60 180

Total female groups 192 576• 18-35 male

groups 48 - - 48 144

Total male groups 48 144

Groups can be formed according to marital status for 15-29 years old.