相信大家在阅读数据手册的时候都看到Accuracy和Precision这两个词，你能否准确的区别它们，这样能够让你更好的理解数据手册的定义。
Accuracy
Accuracy is how close a measured value is to the actual (true) value.
Precision
Precision is how close the measured values are to each other.
准确度（Accuracy）：指在一定实验条件下多次测定的平均值与真值相符合的程度，以误差来表示。它用来表示系统误差的大小。
精密度（Precision）：是指多次重复测定同一量时各测定值之间彼此相符合的程度。表征测定过程中随机误差的大小。
精确度=准确度+精密度
可用下图表示：

Accuracy and precision in binary classification
"Accuracy" is also used as a statistical measure of how well a binary classification test correctly identifies or excludes a condition.
That is, the accuracy is the proportion of true results (both true positives and true negatives) in the population. It is a parameter of the test
On the other hand, precision is defined as the proportion of the true positives against all the positive results (both true positives and false positives)

from:http://www.keyanshequ.com/thread-336-1-1.html