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Example of Implicit Stratification |
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| Sampling frame of 14 hypothetical refugee camps in the sampling universe (date of establishment) |
Population |
Clusters allocated by PPS (total n = 60) |
Implicit stratification pairs for analysis (n=30) |
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| Explicit stratum 1: No food distributions during recall period |
42 000 |
27 |
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| Camp Romeo (May 2003) |
12 000 |
8 (c1†-c8) |
P1.1‡ (c1,c2), P1.2 (c3,c4), P1.3 (c5,c6), P1.4 (c7,c8) |
| Camp Delta (July 2003) |
8000 |
5 (c9-c13) |
P1.5 (c9,c10), P1.6 (c11,c12) |
| Camp Tango (January 2004) |
3000 |
2 (c14-c15) |
P1.7 (c13,c14) |
| Camp Whiskey (May 2004) |
6000 |
4 (c16-c19) |
P1.8 (c15,c16), P1.9 (c17,c18) |
| Camp Alpha (November 2004) |
4000 |
3 (c20-c22) |
P1.10 (c19,c20), P1.11 (c21,c22) |
| Camp Charlie (February 2005) |
9000 |
5 (c23-c27) |
P1.12 (c23,c24), P1.13 (c25,c26,c27) |
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| Explicit stratum 2: One food distribution during recall period |
27 000 |
17 |
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| Camp November (March 2003) |
2000 |
1 (c28) |
P2.1 (c28,c29) |
| Camp India (April 2003) |
8000 |
5 (c29-c33) |
P2.2 (c30, c31), P2.3 (c32,c33) |
| Camp Victor (August 2003) |
7000 |
4 (c34-37) |
P2.4 (c34,c35), P2.5 (c36,c37) |
| Camp Oscar (June 2004) |
10 000 |
7 (c38-c44) |
P2.6 (c38,c39), P2.7 (c40,c41), P2.8 (c42,c43,c44) |
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| Explicit stratum 3: Two food distributions during recall period |
26 000 |
16 |
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| Camp Bravo (April 2003) |
6000 |
4 (c45-c48) |
P3.1 (c45,c46), P3.2 (c47,c48) |
| Camp Sierra (November 2003) |
1000 |
1 (c49) |
P3.3 (c49,c50) |
| Camp Foxtrot (March 2004) |
3000 |
2 (c50-c51) |
P3.4 (c51, c52) |
| Camp Uniform (December 2004) |
16 000 |
9 (c52-c60) |
P3.5 (c53,c54), P3.6 (c55,c56), P3.7 (c57,c58), P3.8(c59,c60) |
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† c1 = cluster 1, c2 = cluster 2, etc. ‡P1.1 = explicit stratum 1, implicit pair 1, etc. | |||
Working Group for Mortality Estimation in Emergencies Emerging Themes in Epidemiology 2007 4:9 doi:10.1186/1742-7622-4-9 |
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