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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.

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Presentation on theme: "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."— Presentation transcript:

1 Sample Selection: SAFE Project

2 Study Design 3-Level Multi Site Cluster Randomized Trial (CRT) with power=0.80; alpha=0.05; and r= arms with different combinations of intervention, to be measured at baseline and endline in 18 months apart Arm 1Arm 2Arm 3 Clinic Community campaigning Female groups Male groups

3 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 1Arm 2 Clinic Community campaigning Female groups Male groups Arm 2Arm 3 Clinic Community campaigning Female groups

4 All common intervention components across arms, i.e., clinic, community campaigning and female group sessions must be similar across arms of all sites for ensuring comparability Standardization of intervention components

5 Study Subjects and Sample Size Age group and sex Marital status Effect variable MDESClusters for 3 arms Cluster size (N) Cluster size (N) with 20% over- sampling No. of sites (K) Sample-3 arms females Married; Unmarried Marriage 45% females Married; Unmarried Violence exposure 55% males Married; Unmarried SRHR Knowledge and attitudes 55% Total Female sample ( )4212 Total Male sample 1458 Total sample ( )5670

6 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….

7 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

8 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

9 Understanding the temporary settlement/slum setting Three study sites include 3 UPHCP referral clinics- Mohammadpur Landmark: Sikder Medical, Poolpar No. of slums-8 ; Population-30,285 Bashabo Landmark: Buddha Mandir No. of slums-7; Population-14,200 (MS will identify more slum population) Mohakhali Landmark: Mohakhali Flyover No. of slums-5; Population-30,500

10 Understanding the temporary settlement/slum setting Three study sites include 3 UPHCP referral clinics- Mohammadpur Landmark: Sikder Medical, Poolpar No. of slums-8 ; Population-30,285 Bashabo Landmark: Buddha Mandir No. of slums-7; Population-14,200 (MS will identify more slum population) Mohakhali Landmark: Mohakhali Flyover No. of slums-5; Population-30,500

11 Minimum population requirement per site Each site must have 25,000-30,000 population (5,000 to 6,000 households) because 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 years [19500 x 10% years old x 50% female]

12 Each of the three site has 1 clinic and 5 to 8 slums Mohammadpur clinic [Poolpar] Bashabo clinic [Mandir] Mohakhali clinic [Flyover] Site-1Site-2Site-3 Slum 1 Slum 2 Slum 3 Slum 4 Slum 5

13 Identification of clusters across 3 arms Mohakhali Clinic Arm 1 Arm 2 Arm 3

14 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

15 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

16 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

17 Clusters for survey and groups for intervention per site across 3 arms Mohakhali Clinic Arm 1 Arm 2 Arm 3 80 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

18 Number of female and male groups Group characteristics Arm 1Arm 2Arm 3Total groups in each site Total groups in 3 sites female groups female groups female groups Total female groups male groups Total male groups48144 Groups can be formed according to marital status for years old.


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