Select the purpose of Hong Thai commune, An Duong district to intervene: Use the formula for calculating the sample size for the difference between the two ratios: n = Z2 (, β) P1 (1-p1) + P2 (1-p2) (2) Inside: (P1 - P2) 2 N: is the sample size P1 = rate of asthma control before intervention (5%) P2 = rate of asthma control after intervention (30%) Calculate n = 61 patients.