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A pattern similar to a dart board with few concentric circles shown in white color on a red background. In the innermost circle, there are four black points on the circumference showing the positions of a restaurant. They are far apart from each other.
A GPS system attempts to locate a restaurant at the center of the bull’s-eye. The black dots represent each attempt to pinpoint the location of the restaurant. The dots are spread out quite far apart from one another, indicating low precision, but they are each rather close to the actual location of the restaurant, indicating high accuracy. (credit: Dark Evil)
A pattern similar to a dart board with a few concentric circles shown in white color on a red background. Near the outermost white circles there are four black points showing the positions of a restaurant. The black points are very close to each other.
In this figure, the dots are concentrated rather closely to one another, indicating high precision, but they are rather far away from the actual location of the restaurant, indicating low accuracy. (credit: Dark Evil)

Accuracy, precision, and uncertainty

The degree of accuracy and precision of a measuring system are related to the uncertainty    in the measurements. Uncertainty is a quantitative measure of how much your measured values deviate from a standard or expected value. If your measurements are not very accurate or precise, then the uncertainty of your values will be very high. In more general terms, uncertainty can be thought of as a disclaimer for your measured values. For example, if someone asked you to provide the mileage on your car, you might say that it is 45,000 miles, plus or minus 500 miles. The plus or minus amount is the uncertainty in your value. That is, you are indicating that the actual mileage of your car might be as low as 44,500 miles or as high as 45,500 miles, or anywhere in between. All measurements contain some amount of uncertainty. In our example of measuring the length of the paper, we might say that the length of the paper is 11 in., plus or minus 0.2 in. The uncertainty in a measurement, A size 12{A} {} , is often denoted as δA size 12{δA} {} (“delta A size 12{A} {} ”), so the measurement result would be recorded as A ± δA size 12{ +- δA } {} . In our paper example, the length of the paper could be expressed as 11  in. ± 0. 2 . size 12{ +- 0 "." 2 "." } {}

The factors contributing to uncertainty in a measurement include:

  1. Limitations of the measuring device,
  2. The skill of the person making the measurement,
  3. Irregularities in the object being measured,
  4. Any other factors that affect the outcome (highly dependent on the situation).

In our example, such factors contributing to the uncertainty could be the following: the smallest division on the ruler is 0.1 in., the person using the ruler has bad eyesight, or one side of the paper is slightly longer than the other. At any rate, the uncertainty in a measurement must be based on a careful consideration of all the factors that might contribute and their possible effects.

Making connections: Real-world connections – fevers or chills?

Uncertainty is a critical piece of information, both in physics and in many other real-world applications. Imagine you are caring for a sick child. You suspect the child has a fever, so you check his or her temperature with a thermometer. What if the uncertainty of the thermometer were 3 . C size 12{3 "." 0°C} {} ? If the child’s temperature reading was 37 . C size 12{"37" "." 0°C} {} (which is normal body temperature), the “true” temperature could be anywhere from a hypothermic 34 . C size 12{"34" "." 0°C} {} to a dangerously high 40 . C size 12{"40" "." 0°C} {} . A thermometer with an uncertainty of 3 . C size 12{3 "." 0°C} {} would be useless.

Questions & Answers

a rare fraction and adjacent contraction of a sound wave are travelling in air and are separated by distance of 15cm, taken that velocity sound is 330ms what is the frequency?
Jennifer Reply
u need answer
Abbas
yes pls
Jennifer
Is ans 64/3
yuvraaj
2200hertz
chiadikaobi
what is speed and velocity
Yaseer Reply
speed is scaler quantity and velocity is vector quantity speed has only magnitude and velocity has magnitude+direction both speed and velocity has same unit m/s
shubham
I am finding it hard to draw the velocity time graph, please can anyone assist me to know how to draw it, please?
bona
explain and draw how to measure length when using ruler, micrometer screw gauge and vernnier calliper
gift Reply
Calculate the average velocity in time interval 6sec to 12sec and determine the instantaneous velocity
Lekiisi Reply
v/6
chiadikaobi
the force is not constant in this case of tow car collide for short period of time ..why is the force is not constant?
Abel Reply
hmmm
Fortune
calculate the average velocity in time interval 6sec to 12sec ad determine the instantaneous velocity
Lekiisi
meaning of the term si units
Chali Reply
what what causes electric current
Chali
what what causes electric current
Chali
Charges(electron)
Caleb
Systeme international unitq@1qa@aaq
Caleb
Correct one international system of units.
Caleb
electric dynamo
albert
Electric dynamo is the sources of electric magnetic forces which utilize electromagnetic induction.
albert
A stone is dropped down a well, if it take 5 seconds to reach the water, how dip is the well
Mollamin Reply
125m dip
chiadikaobi
an aircraft at as steady velocity of 70m/so eastwards at a height of 800me drops a package of supplies .a, how long will it take for the package to rich the ground? b, how fast will it be going as it lands?
Ng Reply
what is hypothesis theory law
Tamba
144.57m/s
chiadikaobi
physics is the science of measurement
Jide Reply
What is physics
Victor Reply
what is physics
Obaro
Good question! Physics is the study of the nature world . Does this help?
Yonn
physics is the study of matter in relations to energy.
Enoch
physics is the science of measurements
Jide
physics is a science concern with nature and properties of matter and energy
Ugomma
what is a parallelogram law of motion?
Nancy
describe how you would find the area of an irregular shaped body?
Chali
physics is the study of natural phenomena at their most fundamental level
Yaseer
Definition for physics
Adesola Reply
It deal with matter and relation to energy
Soughie
physics is the Study of matter in relation to energy.
albert
physics is a natural science that study matter its behaviour and relation to energy.
mohammed
physic tells us more about quantities and measurement also
Kelly
life as we know it that can be measured and calculated
Jesus
what is a reference frame
Chukwu Reply
what is anatomy in relation to physics
Mubarak Reply
how does half life exist
Humble Reply
 The amount of time it takes a radioactive isotope to decay into a stable isotope is different for each radioactive isotope, and is characterized by its “half-life”. An isotope's half-life is the amount of time it takes for half the number of atoms of that isotope to decay to another isotope.
Nardine
what is the difference between Mass and weight
Pjustin
mass is constant while weight varies. unit of mass is kg, unit of weight is newton
Faith
how can a coin float in water and what principle governs it
Mercy Reply
in my opinion that work of surface tension but restrictions on coin is that coin do not break surface energy of molecules but some days before scientists prove that's another types of force
Aman
which force hold floating coins together thats my confusion
Aman
Practice Key Terms 6

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Source:  OpenStax, College physics. OpenStax CNX. Jul 27, 2015 Download for free at http://legacy.cnx.org/content/col11406/1.9
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