1. Determining Sampling Methods CEI 2015.0 Implementing the Reproductive Health Assessment Toolkit for Conflict-Affected Women November 5, 2006

2. Objectives At end of session, you will be able to: Understand importance of sampling Describe advantages/disadvantages of random and cluster sampling Obtain hands on sampling experience

3. What is Sampling? The procedure by which some members of a population are selected as representative of the entire population

4. Importance of Sampling Good sampling = representative data!! –Make reasonable inferences Decreases costs Speeds up data collection Balance feasibility and precision

5. Toolkit Sampling Sampling unit = households (HH) One woman of reproductive age (WRA) per HH Choose random or cluster sampling Modify based on needs

6. Area

8. Geographic Bounds Well-defined –Refugee or IDP camp –Groups of camps –Villages or towns where displaced people live Use a map

9. Random Sampling AdvantageDisadvantage Random More precise Smaller sample size Complete HH listing Could use more resources More travel/time

10. Cluster Sampling AdvantageDisadvantage Cluster No/incomplete HH listing Could use less resources Less travel Less precise Larger sample size

11. Random vs Cluster AdvantageDisadvantage Random More precise Smaller sample size Complete HH listing Could use more resources More travel/time Cluster No/incomplete HH listing Could use less resources Less travel Less precise Larger sample size

12. Random Sampling Assumptions: –Prevalence rate of 50% –95% confidence intervals +/- 5% –Response rate of 80% 400 completed interviews  must sample 500 HH

13. Random Sampling Steps Step 1. Obtain HH lists Step 2. Identify HHs and select sample HHs to be surveyed Step 3. Select one WRA with each selected HH to be surveyed

14. Sample Household List ID#NameAgeFamily size # WRADate of arrival 2416X316211/27/2001 2723X26418/22/1999 2714X43414/21/2001 2448X53507/1/2000 2578X284211/20/2000 2463X34517/5/1998 Household removed before selection because no WRA

15. Practice Exercise: Random

16. Random: Table 1 CampHouseholdsHousehold proportion Sample size Camp 1367 Camp 2405 Camp 3245 Camp 4271 Camp 5350 Total 1638 367/1638 =22.4%

17. Random: Table 1 CampHouseholdsHousehold proportion Sample size Camp 1367367/1638 = 22.4% Camp 2405405/1638 = 24.7% Camp 3245245/1638 = 15.0% Camp 4271271/1638 = 16.5% Camp 5350350/1638 = 21.4% Total 1638100.0%.224 x 500= 112

18. Random: Table 1 CampHouseholdsHousehold proportion Sample size Camp 1367367/1638 = 22.4%.224 x 500= 112 Camp 2405405/1638 = 24.7%.247 x 500= 124 Camp 3245245/1638 = 15.0%.150 x 500= 75 Camp 4271271/1638 = 16.5%.165 x 500= 83 Camp 5350350/1638 = 21.4%.214 x 500= 107 Total 1638100.0%501

19. Random Numbers Table OR use computer applications For both random and cluster Example: Randomly select 112 HHs from 367 HHs for Camp 1. –How many digits -> 001-367, need 3 digits –Choose a direction -> decide to go right –Choose starting point –Read the number of digits –Repeat until 112 HHs selcted

20. Random Numbers Table ABCDE 184506992656303402649 259521443710084443904 357116779938896684167 426818047049478538411 507393114399734823226 689852463505434486357 437 (discard not in range)

21. Random Numbers Table ABCDE 184506992656303402649 259521443710084443904 357116779938896684167 426818047049478538411 507393114399734823226 689852463505434486357 100 HH is selected for sample

22. Cluster Sampling Can not guarantee precision Assumptions: –Response rate of 80% –At least 25 clusters with 25 HH in each Probability proportional to size (PPS) 500 completed surveys  so sample 625 HHs

23. Cluster Sampling Step 1. Define clusters within geographic boundaries Step 2. Determine the number of HHs within each cluster Step 3. Select the clusters to be surveyed Step 4. Select the HHs within each cluster to be surveyed Step 5. Select one WRA within each selected HH to be surveyed

24. Practice Exercise: Cluster

25. Cluster: Step 3 ClusterHH in clusterCumulative # of HHs Range 126 1-26 2305627-56 3278357-83 45013384-133 531164134-164 628192165-192 735227193-227 8 (etc... )42269228-269

26. Cluster: Step 3 Sampling interval = cumulative # of HH divided by 25 clusters –Ex: 970/25 clusters = 39 (sampling interval) Randomly select number within sampling interval range –Ex: 01-39 = 31 is starting number Find where this number falls within range and cluster selected

27. Cluster: Step 3, select 1 st cluster ClusterHH in clusterCumulative # of HHs Range 128 1-28 2326029-60 36512561-125 448173126-173 525198174-198 629227199-227 737264228-264 8 (etc... )34298265-298 31 falls within range Cluster 2 selected for sample

28. Cluster: Step 3 Add sampling interval to first number: –Ex: 31 + 39 = 70 Find where this number falls within range and cluster selected Continue until 25 clusters selected

29. Cluster: Step 3, select 2 nd cluster ClusterHH in clusterCumulative # of HHs Range 128 1-28 2326029-60 36512561-125 448173126-173 525198174-198 629227199-227 737264228-264 8 (etc... )34298265-298 70 falls within range Cluster 3 selected for sample

30. Cluster: Step 3, select 3 rd cluster ClusterHH in clusterCumulative # of HHs Range 128 1-28 2326029-60 36512561-125 448173126-173 525198174-198 629227199-227 737264228-264 8 (etc... )34298265-298 70 + 39=109 falls within range Cluster 3 selected again for sample

31. Random vs Cluster AdvantageDisadvantage Random More precise Smaller sample size Complete HH listing Could use more resources More travel/time Cluster No/incomplete HH listing Could use less resources Less travel Less precise Larger sample size

32. DRH Technical Assistance Review sampling plan Consult on different sampling methods

33. www.cdc.gov/reproductivehealth/Refugee Reproductive Health Assessment Toolkit for Conflict-Affected Women