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六.四格表的确切概率法四格表的确切概率法又称四格表概率的直接计算法,此法不必查表,可以直接求出概率(P)。它特别适用于以下情况:①四格表X~2检验得出的概率接近显著性水平,难以下结论时;②总例数少于40例,尤其当两样本含量相差悬殊,同时两样本阳性数之和与阴性数之和相差也悬殊时;③样本实际频数a、b、c、d中出现任何小值(如0,1,2,……等),理论频数中出现小于5甚至小于1,而不宜计算X~(?)值时。概率的计算方法是将四格表的周边合计固定表内四个实际频数的组合共有“周边合计中的最小数
Six. The exact probability of the four grid table The exact probability method of the four grid table, also known as the direct calculation method of the probability of the four grid table, this method does not have to look up the table, you can directly find the probability (P). It is particularly applicable to the following situations: 1 The probability of the four-square table X~2 test is close to the level of significance, and it is difficult to draw conclusions; 2 The total number of cases is less than 40 cases, especially when the two sample contents differ greatly, and the two samples are positive. The difference between the sum of numbers and the number of negatives is also very different; 3 the actual frequency of the sample a, b, c, d appear any small value (such as 0,1,2, ..., etc.), the theoretical frequency appears less than 5 or even less than 1, not when calculating X ~ (?) When. The probability is calculated by combining the four actual frequency combinations within the perimeter total fixed table of the four-grid table.