Big and small of residual error and rule of signchange was observed with inspection method of residual error, and if it had system error or rough error and so on was identified.
采用残余误差观察法观察残差图中各个残余误差大小和符号变化规律，可直接判断有无系统误差。
2
If the listener is not paying attention, it's your sign to shorten the story or change direction.
如果听者不专心，这表明你应该缩短故事或改变话题。
3
And, if it is a signed multiply, the sign could even change on truncation!