Month: December 2008

“Accuracy” vs. “Precision”

Nouns, Versus

I frequently hear people confuse accuracy and precision.

Problem:
These two nouns are not synonyms, at least not in science.

Explanation:
The scientific definition of the noun “accuracy” is the degree to which a measurement agrees with that measurement’s standard value.

The scientific definition of the noun “precision” is the degree to which a set of measurements of the same sample agree with that set’s mean.

Imagine an archery target, and imagine an archer shooting arrows at that target.

The closer that an arrow lands to the center of the target (the bull’s eye), the more accurate is the shot.

In contrast, if an archer can shoot several arrows that all land in almost the same location, then one can say that the archer is precise.

An archer can be accurate simply by the fact that bull’s eye is the mean of the points at which all of his or her arrows land.

An archer can be precise simply by the fact that all of his or her arrows land in the same location.

Precision speaks to reproducibility and standard deviation within the sample. Higher precision in a trial (e.g., in shooting a set of arrows) refers to greater reproducibility and smaller standard deviation.

Accuracy speaks to nearness to the target. Higher accuracy in a trial (e.g., in shooting a set of arrows) refers to less distance between the target location or value and the mean of the actual locations or values.

This discussion has these implications:

  • A trial can be accurate but not precise.
  • A trial can be precise but not accurate.
  • An ideal trial is both accurate and precise.
  • One can make a calculated adjustment for a trial that is precise but not accurate (that is, a trial that is biased), if one knows the degree of inaccuracy (the degree of bias).
  • One can ignore a trial’s imprecision (the degree of variability) in a trial that is accurate but not precise, if one’s primary interest is that the mean within the trial is very close to the goal or target.

Solution:
Think “nearness to a goal” when thinking of accuracy. Think “reproducibility” when thinking of precision.

“… you will not feel any air being blowned …”

Common English Blunders, Outsider's Perspective, Verbs

I saw this on a website this morning.

Problem:
The past participle is a nonsense word.

Explanation:
I was researching which way a ceiling fan should turn in the winter versus the summer when I discovered this.

The full sentence was “In the winter, you will not feel any air being blowned to you since it will be pulled up to the ceiling.”

Admittedly, seeing the past participle of the verb “blow” as B-L-O-W-N-E-D is essentially humorous, but there is instructional value in discussing this blunder.

The verb “blow” has these basic forms:

  • Blow — present simple, as in “The fan at top speed can blow the dust away.”
  • Blew — preterite, as in “He blew up the balloon.”
  • Blown — past participle, as in “She has blown it out of proportion.”
  • Blowing — present continuous, as in “The wind is not blowing.”

A common English blunder for young children and for those who are learning English as a second language is to write or say “blowed” — spelled B-L-O-W-E-D — as the preterite or past participle of the verb “blow”.

In other words, the blunder is to add E-D to the present simple form because many preterites and past participles are formed in this way. For example, the verb “form” has “formed” — spelled F-O-R-M-E-D — as its preterite and as its past participle.

Here are examples of use of the nonsense word “blowed”:

  • As a preterite:
    • “He blowed up at her.”
    • “The wind blowed last night!”
  • As a past participle:
    • “She has blowed her chances.”
    • “If you guys had not blowed the money in Atlantic City, you would not be begging me for a loan today.”

For fun, I searched Google for each of the following (without the quotation marks) and got about the indicated numbers of matches:

  • “blew” — 19,800,000 matches
  • “blown” — 33,100,000 matches
  • “blowed” — 541,000 matches

This tells me that Web authors have used the correct “blew” or the correct “blown” versus the incorrect “blowed” by a ratio of 36.6-to-1 or 61.1-to-1, respectively, each of which is very good, but over a half million instances of “blowed” is nothing about which to brag.

Another blunder is to say or write “blown” as the preterite of the verb “blow”, as in “He blown it.”

I had never heard or seen the word “blowned” until today. I suppose that it would be reasonable to add E-D to the end of B-L-O-W-N, if someone believed that “blown” were the preterite — because some past participles are formed in this way.

For fun, I searched Google for each of the following (without the quotation marks) and got about the indicated numbers of matches:

  • “blown” — 33,100,000 matches
  • “blowned” — 86,400 matches

This tells me that Web authors have used the correct “blown” versus the incorrect “blowned” by a ratio of 383-to-1, which is superb.

Solution:
“… you will not feel any air being blown …”

“Bake” vs. “Roast”

Verbs, Versus

I thought about these two verbs the other day and wondered what the distinction was.

Problem:
Some people use these verbs interchangeably, but they are not quite synonyms.

Explanation:
Some say that roasting specifically applies to meat.

Others say that one can roast vegetables, too.

For example, some say that a roasted potato differs from a baked potato in that the roasted potato is cooked in an oven with liquids poured over it while the baked potato is cooked in an oven without such liquids.

I wondered whether this was the best distinction, so I read the definition of each verb in a dictionary.

The verb “roast” — when it comes to food — specifically means to bake uncovered, and the verb “roast” applies to both meat and other food.

In other words, to roast a potato is to bake it uncovered, usually in an oven.

Whether the potato is cooked with liquids is immaterial to whether it is roasted.

Solution:
Think of roasting as a special way of baking — that is, baking food uncovered.