Table I.

Minimum Detectable Improvements in HTN Control Rate

over-time correlation*	8 barbershops per study-arm	12 barbershops per study-arm
0	15.5%	12.3%
0.1	15.0%	11.9%
0.2	14.6%	11.6%
0.3	14.1%	11.2%
0.4	13.6%	10.8%
0.5	13.1%	10.4%

Percentages are mean differences in HTN control rates between intervention and control barbershops in an experimentally controlled nested cross-sectional design. Calculations assume 100 hypertensive customers per barbershop, 80% power, and 2-sided 5% significance level.

^*Over-time correlation refers to repeat-measure correlation of HTN control rate in a given barbershop