Accuracy Versus Precision（准确率Vs精度）

Accuracy Versus Precision

A surveyor strives for both accuracy and precision.  Many people use the terms “accuracy” and “precision” interchangeably.  However, for those in the surveying profession (as well as other technical and scientific fields), these words have different meanings.  To surveyors, “accuracy” refers to how closely a measurement or observation comes to measuring a "true value," since measurements and observations are always subject to error.  “Precision” refers to how closely repeated measurements or observations come to duplicating measured or observed values. 

对于一个测量员来说，准确率和精度一直是他们为之追求的目标。许多人认为可以交换地使用“准确度”和“精度”这些术语。然而对于那些在测量专业（也和其他技术科学领域一样）中人来说，这些词汇有着不同的意思。对于测量员来说，“准确度”涉及到相对一个真实值，一个测量或观测是多大程度上与它的接近，因为测量和观测总是会产生误差的。“精度”涉及到相对一个重复性的测量的或观测的值，测量的或观测的值彼此之间是多大程度上的相近。

Using four cases of rifle shots fired at a bull’s eye target, each with different results, helps to distinguish the meaning of these two terms.

下面使用四个来复枪在公牛眼型标靶射击，并且每一个标靶有着不同结果的例子来帮助我们去区分这两个术语的意思。

These four sets of rifle shots illustrate the distinction that surveyors make between the terms “accuracy” and “precision,” as applied to surveying measurements and observations. Click image for larger view.

Case 1: Not accurate, not precise:   A shooter stands, aims through the rifle’s telescopic sight, and fires four shots at a target.  Upon examining the target, the shooter sees that all four shots are high or left and scattered all around that part of the target.  These shots were neither accurate (not close to the center) nor precise (not close to each other).

例1：不准确，不精确：
一个射击员站在标靶前，通过来复枪上的瞄准器对着标靶开了四枪，检查这个标靶，这个射击者看到，这四枪，一些偏高，一些偏左，并且相对标靶中心分散着排布。这些射击既不准确(射击点没有靠近靶心）也不精确（射击点彼此也不接近）

Case 2: Precise, not accurate: The shooter assumes a prone position, rests the barrel of the rifle on a support, takes careful aim, holds his breath, and gently squeezes the trigger.  The target shows that these four shots are very close together, but all four are high and to the left of the bull’s eye.  These shots are precise (close together), but not accurate (not close to the center of the target).

例2：精确，不准确：
这个射击员做了一个卧姿，把枪管放在支架上，小心翼翼的瞄准目标，屏住呼吸，轻轻地扣动扳机。这个标靶上展现了这四枪射击点彼此之间是非常靠近，但是这四枪都射击在了牛眼型标靶中心的较高处和左边了。这些射击是精确的（射击点彼此接近），但不准确（射击点没有靠近靶心）

Case 3: Accurate, not precise:  The shooter adjusts the rifle’s telescopic sight and, full of confidence that the problem of inaccuracy has been solved, stands and quickly fires four shots.  Upon studying the target, the four holes are scattered across the target, but the location of each of the four is very close to the bull’s eye.  These shots are accurate, but not precise.

例3：准确，不精确：
射击者调整来复枪上的瞄准器，并且十分自信不准确的问题已经被解决，站稳瞄准后，快速地射击了四枪，通过观察标靶上的射击情况后发现，这四个射击点分散的环绕着标靶中心，但是他们的位置都非常接近牛眼型标靶靶心，这些射击是准确的但是不精确

Case 4: Accurate, precise:  The shooter again assumes a prone position, rests the barrel of the rifle on a support, takes careful aim, holds his breath, and gently squeezes the trigger four times.  This time, the four holes are very close to the center of the target (accurate) and very close together (precise).

例4：准确，精确：
射击者再次做了个卧姿，把枪管放在支架上，小心翼翼的瞄准目标，屏住呼吸，轻轻地扣动扳机四次。这一次，这四个射击点十分的接近标靶中心（准确）并且射击点之间也挨得很近（精确）。

To illustrate the distinction between terms using a surveying example, imagine surveyors very carefully measuring the distance between two survey points about 30 meters (approximately 100 feet) apart 10 times with a measuring tape.  All 10 of the results agree with each other to within two millimeters (less than one-tenth of an inch).  These would be very precise measurements.  However, suppose the tape they used was too long by 10 millimeters.  Then the measurements, even though very precise, would not be accurate.  Other factors that could affect the accuracy or precision of tape measurements include:  incorrect spacing of the marks on the tape, use of the tape at a temperature different from the temperature at which it was calibrated, and use of the tape without the correct tension to control the amount of sag in the tape.

为了阐明这两个术语之间的区别，使用一个测量实例。假想一个观测员使用一个测量尺非常小心地测量了两个观测点之间距离约为30米（大约100英尺）10次。所有的测量结果在2毫米（小于十分之一英尺）的误差范围内彼此很吻合，这些是非常精确的测量。然而假设他们用的这个测量尺长了10毫米，那么这个测量即使非常精确，但却不准确。其他会影响测量尺的准确度和精度的因素包括：测量尺上不正确的标记刻度；使用测量尺在没有校准温度的情况进行了测量；使用测量尺在测量时没有拉直张紧控制好测量尺的下垂量

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对于Accuracy 和 Precision按照中文翻译确实有很大相近之处，最近在做有关检测的任务，需要用到这些指标，在网上查了一堆资料，感觉有些杂，好多都是文字说明，有点绕，wiki上也是一堆文字，不过感觉还不错，总体的感觉是中文资料确实没有英文的好，这点不得不承认，看到这篇英文，感觉写的太好了，读完之后（主要是那四幅图太直观明了）索性把它翻译一下放在这里方便大家参考，这是我第一次译文，可能会有一些小问题，参阅者如有发现望指正。

在区分Accuracy 和 Precision时看到不错的资料链接放在于此：

原文链接：https://celebrating200years.noaa.gov/magazine/tct/tct_side1.html

wiki：https://en.wikipedia.org/wiki/Accuracy_and_precision

很不错的中文blog:https://blog.csdn.net/wokaowokaowokao12345/article/details/72830242