样本标准偏差的平方,即(“2”是表示平方):S2=(X-X平均)2/(n-1)两组数据就能得到两个S2值,S大2和S小2F=S大2/S小2由表中f大和f小(f为自由度n-1),查得F表,然后计算的F值与查表得到的F表值比较,如果F F表 表明两组数据没有显著差异;F F表 表明两组数据存在显著差异置信度95%时F值(单边)f大f小2345678910234567891019.09.556.945.795.144.744.464.264.103.0019.169.286.595.414.764.354.073.863.713.6019.259.126.395.194.534.123.843.633.482.3719.309.016.265.054.393.973.693.333.2119.338.946.164.954.283.873.583.373.222.1019.368.886.094.884.213.793.503.293.142.0119.378.846.044.824.513.733.443.233.071.9419.388.816.004.783.683.393.183.021.8819.398.785.964.063.343.132.971.8319.58.535.634.363.672.932.712.541.00为大方差数据的自由度; 为小方差数据的自由度。