文献[1]、[2]介绍了四格表中一实际频数为0(如表1)的确切概率计算法(简称A法),用公式(1)计算实测四格表的概率。表1 有一实际频数为0的四格表的模式 The literature [1], [2] introduced an exact probability calculation method (abbreviated as A method) with an actual frequency of 0 (as shown in Table 1) in the four-square table, and used formula (1) to calculate the probability of the measured four-square table. Table 1 has a four-grid table with an actual frequency of 0