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Table 2 Sample size calculations

From: Conquering hypertension in Vietnam—solutions at grassroots level: study protocol of a cluster randomized controlled trial

Power Sample size
Unadjusted Cluster-adjusted1 Cluster-adjusted and retention inflated2
0.80 410 522 573
0.85 468 614 674
0.90 548 549 823
  1. Sample size calculations assume an improvement in systolic blood pressure of 8 mmHg in the intervention group and 3 mmHg in the comparison group for a differential, over-time improvement of 5 mmHg. Alpha error is set at 0.05
  2. 1According to approach described by Donner and setting intra-class correlation coefficient at 0.011 based on pilot data
  3. 2Final calculations are inflated by approximately 10% to account for potential loss to follow-up