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General background information

This section will contain a discussion of accuracy, precision, scientific notation, and significant figures.

Accuracy and precision

Let's begin with a brief discussion of accuracy and precision. These two terms are often confused in everyday conversation, but they have very differentmeanings in the world of science and engineering.

Accuracy

In science and engineering, the accuracy of a measurement system is the degree of closeness of measurements of a quantity to its actual (true) value.

Precision

The precision of a measurement system (also called reproducibility or repeatability) is the degree to which repeated measurements under unchangedconditions show the same result.

Four possibilities

A measurement system can be:

  • Both accurate and precise.
  • Accurate but not precise.
  • Precise but not accurate.
  • Neither accurate nor precise.

A hypothetical experiment

Consider an experiment where a firearm is clamped into a fixture, very carefully aimed at a bulls eye on a downrange target, and fired six times.(Although you may never have seen or touched a firearm, you probably have a pretty good idea of how they behave.)

If the six holes produced by the bullets in the target fall in a tight cluster in the bulls eye, the system can be considered to be both accurate andprecise.

If all of the holes fall in the general area of the bulls eye but the cluster is not very tight, the system can be considered to be accurate but not precise.

If all of the holes fall in a tight cluster but the cluster is some distance from the bulls eye, the system can be considered to be precise but not accurate.

If the holes are scattered across a wide area of the target, the system can be considered to be neither accurate nor precise.

Another use of the word precision

Another use of the word precision, which will be important in this module, is based on the concept that the precision of a measurement describes the unitsthat you use to measure something.

How tall are you?

For example, if you tell someone that you are about five feet tall, that wouldn't be very precise. If you told someone that you are 62 inches tall, thatwould be more precise. If you told someone that you are 62.3 inches tall, that would be even more precise, and if you told someone that you are 62.37 inchestall, that would be very precise for a measurement of that nature.

The smaller the unit...

The smaller the unit you use to measure with, the more precise the measurement can be. For example, assume that you measure someone's height with atactile measuring stick that is longer than the person is tall. Assume also that the measuring stick is graduated only in feet. In that case, the best that youcould hope for would be to get the measurement correct to the nearest foot and perhaps estimate a second digit to the nearest tenth of a foot.

One-inch graduations

On the other hand, if the measuring stick is graduated in inches and you are careful, you should be able to get the measurement correct to the nearest inchand perhaps estimate another digit to the nearest tenth of an inch. The second measurement using the one-inch graduations would be more precise than the firstusing the one-foot graduations.

Questions & Answers

where we get a research paper on Nano chemistry....?
Maira Reply
nanopartical of organic/inorganic / physical chemistry , pdf / thesis / review
Ali
what are the products of Nano chemistry?
Maira Reply
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
learn
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
learn
Google
da
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Bhagvanji
hey
Giriraj
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
revolt
da
Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
Jyoti Reply
ya I also want to know the raman spectra
Bhagvanji
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
Nasa has use it in the 60's, copper as water purification in the moon travel.
Alexandre
nanocopper obvius
Alexandre
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
Hafiz
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
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Source:  OpenStax, Accessible physics concepts for blind students. OpenStax CNX. Oct 02, 2015 Download for free at https://legacy.cnx.org/content/col11294/1.36
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