Sample Size
Stroke
STROKE
Assuming 31 patients per period (6 months) per hospital, 51 hospitals, a 0.03 intraclass correlation coefficient, and a 19% reperfusion treatment rate at baseline, we expected a total of 6324 patients would provide 90% statistical power for detecting a 30% improvement in the primary outcomes (from 19% to 25%) at a 2-sided α level of 0.05. The 19% rate was based on the Chinese Stroke Center Alliance data up to March 2018.