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

Table 2 Sample size calculations

Power	Sample size
Power	Unadjusted	Cluster-adjusted¹	Cluster-adjusted and retention inflated²
0.80	410	522	573
0.85	468	614	674
0.90	548	549	823

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
¹According to approach described by Donner and setting intra-class correlation coefficient at 0.011 based on pilot data
²Final calculations are inflated by approximately 10% to account for potential loss to follow-up

ISSN: 1745-6215