A false positive or negative error rate is impossible to measure because these are such rare events.
一个错误的正或负误差率是不可能衡量的，因为这些是很罕见的事件。
a rare occurrence, sight, visitor
稀罕事、 罕见的景象、 稀客
The Study on the Issues of Scenario Evolvement in Real-time Decision Making of Infrequent Fatal Emergencies
罕见重大突发事件应急实时决策中的情景演变
An act or event so extraordinary or rare as to inspire wonder.
奇观，奇迹奇特的或罕见的引起人们惊叹的事件或行为
Don't worry about such improbabilities as earthquakes.
不必为像地震这类罕见的事情而担心。
Don' worry about such inprobabilities as earthquakes
不必为象地震这样罕见的事担心
But the rarer three-and four-lepton events suggest a complex cascade of transformations that may prove difficult to unravel.
但是，比较罕见的三轻子和四轻子事件却暗含着有一个复杂的级联衰变，这是很难解释的。
In imperial harems, it was a common thing that the empress and concubines fought for the love of the emperor.
在帝王的后宫中, 六宫争宠的事并不罕见。
It is very unusual for three own goals to be scored in one match at international level.
乌龙球“帽子戏法”在国际水平的赛事中极为罕见。
This may even lead to death, like suicide and manslaughter, and such cases are not rare in China.
甚至可能导致死亡，如自杀和杀人。这类事件在中国并不罕见。
had been occasioned by an event which was more or less rare --
主要是由一件多少有些稀罕的事情引起的??
He has a nose of unusual size.
他有个罕见的大鼻子。
This is an infrequent stamp.
这是一张罕见的邮票。
I saw an unusual white elephant.
我看到一只罕见的白象。
It is a rather rare ailment.
这是一种比较罕见的疾
Frank had his churlish delicacies.
富兰克有罕见的温情。
The Ethical Choice of Drug and Health Policy for Rare Diseases under the Condition of Market Economy
市场经济条件下罕见病医药卫生政策的伦理选择
Although such appointments are common in criminal proceedings, they are rare in administrative law.
虽然在刑事诉讼中指定律师是惯常的做法，但在行政法中仍属罕见。