Minitab 19 计算Cpk问题

我在使用MINITAB19 进行过程能力分析时，Cpk、Ppk计算结果都是*，有没有知道是怎么回事的？




计算过程如下：
统计>>质量工具>>能力分析>>正态










数据如下：
直径
74.03
74.002
74.019
73.992
74.008
73.995
73.992
74.001
74.011
74.004
73.988
74.024
74.021
74.005
74.002
74.002
73.996
73.993
74.015
74.009
73.992
74.007
74.015
73.989
74.014
74.009
73.994
73.997
73.985
73.993
73.995
74.006
73.994
74
74.005
73.985
74.003
73.993
74.015
73.988
74.008
73.995
74.009
74.005
74.004
73.998
74
73.99
74.007
73.995
73.994
73.998
73.994
73.995
73.99
74.004
74
74.007
74
73.996
73.983
74.002
73.998
73.997
74.012
74.006
73.967
73.994
74
73.984
74.012
74.014
73.998
73.999
74.007
74
73.984
74.005
73.998
73.996
73.994
74.012
73.986
74.005
74.007
74.006
74.01
74.018
74.003
74
73.984
74.002
74.003
74.005
73.997
74
74.01
74.013
74.02
74.003
73.982
74.001
74.015
74.005
73.996
74.004
73.999
73.99
74.006
74.009
74.01
73.989
73.99
74.009
74.014
74.015
74.008
73.993
74
74.01
73.982
73.984
73.995
74.017
74.013