关于卡方分析

下面的信息是Minitab run出的结果，请高人指点为什么这组数据结果是接近无效？
用卡方分析对数据有什么要求吗？谢谢
Expected counts are printed below observed counts
Chi-Square contributions are printed below expected counts

好 中 坏 Total
1 117 3 0 120
91.76 27.65 0.59
6.940 21.973 0.588

2 39 44 1 84
64.24 19.35 0.41
9.914 31.389 0.840

Total 156 47 1 204

Chi-Sq = 71.644, DF = 2
WARNING: 2 cells with expected counts less than 1. Chi-Square approximation
probably invalid.
2 cells with expected counts less than 5.谢谢