Accuracy tells us how close

準確度是指

a particular measurement is to the correct value.

測量出的數據有多接近正確的數值

For instance,

舉例來說

how close is the reading of a thermometer to the actual temperature?

溫度計顯示出的溫度和真實的氣溫有多少誤差?

Precision is the consistency of repeated measurement.

精密度則是指多次測量結果的一致性

In other words, are the results consistent

也就是說，每次測量時

each time something is measured?

結果是否都相同?

The more consistent the results,

得到的結果越一致

the more precise the measurement.

表示精密度越高

It is possible to have a precise measurement that is not accurate.

有可能出現高精密度而低準確度的情況

It is also possible to have an accurate measurement that is not precise.

也可能會是高準確度卻低精密度的結果

The best measurements are both accurate and precise!

所以最好的測量方式還是兩者兼具

Let us look more closely at the difference between accuracy and

讓我們進一步解釋準確度和精密度的不同

precision using an archer and target.

舉一個弓箭手和箭靶的例子

The archer is accurate when he hits the bull's eye.

當弓箭手正中紅心，代表他的射擊很準確

He is precise when he can consistently hit the same spot on the target,

當他持續射中靶上的同一區域，表示他很精確

in this case the bull's eye, over and over again.

在這個例子中，他一次又一次擊中

This archer is both accurate (he hits the bull's eye) and

表示這個弓箭手兼具準確度 (他正中紅心) 和

precise (he is able to hit the same area of the bull's eye repeatedly).

精密度 (他能不斷擊中同一區域)

It is also possible for the archer to be precise, but inaccurate.

也有可能這個弓箭手射擊精密，但不準確

If he misses the bull's eye, he is inaccurate; he has missed the mark.

如果他沒正中紅心，表示他射得不準確，偏離目標

But if he can consistently and

但如果他可以持續且

repeatedly hit the target in the same place,

重複的擊中同樣的地方

even if it is not the bull's eye, he is precise.

即使不是在標靶中心， 他仍是精確的

On the other hand, the archer may be accurate, but not precise.

反過來說，弓箭手也有可能射擊準確，卻不精密

If he strikes the bull's eye or right next to the bull's eye,

如果他射中紅心，或只偏離紅心一些的區域

but his arrows are not consistently placed,

但他的箭卻較分散

then the archer is accurate, but not precise.

那表示這個弓箭手是具有準確度，卻沒有精密度

In this case,

在這個例子裡

the arrows would be spread across the bull's eye

箭會散落在紅心附近的區域

rather than clumped together in a small area.

而不是擠在一個極小的範圍裡

If our archer is having a really bad day,

又如果我們的弓箭手今天運氣不太好

he might even be inaccurate and imprecise.

它甚至有可能不準確又不精密

In this case,

範例中

his arrows will strike the target in a random pattern and

他的箭會隨機的擊中標靶，而且

he will not hit the same part of the target time after time.

每一次都無法射中標靶的同一位置