预测正确的比率。
是一个整体的特征。
精确度 Precision
例如数学上的小数点的精确概念，
越是精确，说明度量的结果很稳定，不会有较大的偏差。
但仅仅是对测量结果的刻画，跟真值没有任何关系。
What Is the Difference Between Accuracy and Precision?
https://www.thoughtco.com/difference-between-accuracy-and-precision-609328
Key Takeaways: Accuracy Versus Precision
- Accuracy is how close a value is to its true value. An example would be how close an arrow gets to the bullseye center.
- Precision is how repeatable a measurement is. An example would be how close a second arrow is to the first one (regardless of whether either is near the mark).
- Percent error is used to assess whether sufficiently accurate and precise.
You can think of accuracy and precision in terms of hitting a bullseye. Accurately hitting the target means you are close to the center of the target, even if all of the marks are on different sides of the center. Precisely hitting a target means all the hits are closely spaced, even if they are very far from the center of the target. Measurements which are both precise and accurate are repeatable and very near true values.
Mnemonic To Memorize the Difference
An easy way to remember the difference between accuracy and precision is:
- ACcurate is Correct. (or Close to real value)
- PRecise is Repeating. (or Repeatable)
机器学习中的Bias(偏差)，和Variance(方差)有什么区别和联系？
https://www.zhihu.com/question/27068705