请高人指点

问题1：在信度分析时有警告：The space saver method is used. That is, the covariance matrix is not calculated or used in the analysis.是怎么回事？

问题2：信度结果中Reliability Statistics，Cronbach's Alpha＝.010 是不是太低了，数据看不出什么问题呀。

问题3 ： Item-Total Statistics分析中，当某个变量删除后怎么信度为－0.018，系统提示：The value is negative due to a negative average covariance among items. This violates reliability model assumptions. You may want to check item codings.

说是什么协方差为负违背了信度分析的假设，检查item codings，是指检查数据吗？从数据中也看不出什么问题？请高手指点，在此谢过了。