What is Measurement: Definition and 1000 Discussions

Measurement is the quantification of attributes of an object or event, which can be used to compare with other objects or events. The scope and application of measurement are dependent on the context and discipline. In natural sciences and engineering, measurements do not apply to nominal properties of objects or events, which is consistent with the guidelines of the International vocabulary of metrology published by the International Bureau of Weights and Measures. However, in other fields such as statistics as well as the social and behavioural sciences, measurements can have multiple levels, which would include nominal, ordinal, interval and ratio scales.Measurement is a cornerstone of trade, science, technology and quantitative research in many disciplines. Historically, many measurement systems existed for the varied fields of human existence to facilitate comparisons in these fields. Often these were achieved by local agreements between trading partners or collaborators. Since the 18th century, developments progressed towards unifying, widely accepted standards that resulted in the modern International System of Units (SI). This system reduces all physical measurements to a mathematical combination of seven base units. The science of measurement is pursued in the field of metrology.

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  1. P

    Observational error, identical measurement results

    Homework Statement hello, I have ten results of measurements, all are identical, and how i can count error? it is this: L = ( 20 \pm 0,1 ) cm and all errors, mean squared error etc are 0, how can I count this now?
  2. Lisa!

    Comparing Direct Measurement & Simulation Results: Paired t Test?

    If we measure a quantity with 2 different tools(once by direct measurements and the other time through simulation), is it true if we compare these 2 results together by using paired t test? Does it makes sense ? For example we want to measure the aborbed dose of a patient, so once we measure...
  3. A

    How Can You Measure Light Wavelengths Using Microscope Slides and Rubber Bands?

    In school we somehow measured the minimum and maximum wavelength our eyes could see Unfortunately, all I remember is that we were looking through a slit between jaws of some sort of calipers and used a ruler to do measurements Can anyone please give me an insight of how to set up such...
  4. C

    Theory of Ammeters: Does it Affect Current Measurement?

    <Pic> This is the theory of ammeter give in a book. please read it. Now, my question is that coil will only respond to the current through it i.e. i1. But this is a very small part of total current (Rc >> r). Does this mean that all the moving coil ammeters show wrong current? Please...
  5. D

    No Definite Properties Before Measurement

    Mass, Charge, Spin has definite properties before measurement. What else aside from position, momentum that have NO definite properties before measurement. Is it only position and momentum?
  6. FeDeX_LaTeX

    What is a 'Dollop'? Measurement Equivalence Explained

    Add One "Dollop" Hello; I have tried to be as accurate as possible with my measurements while cooking and I have done fine so far, but what exactly is one 'dollop'? I have been told to add one 'dollop' of mayonnaise and I have no idea what this means. I am assuming it is not a small...
  7. I

    New state function after measurement

    Homework Statement This is an extension to problem 4.55 in Griffiths. The problem is: The electron in a hydrogen atom occupies the combined spin and position state: \lvert \psi \rangle = R_{21} \left(\sqrt{1/3} Y_1^0 \chi_+ + \sqrt{2/3} Y_1^1 \chi_-\right) a) If S_z is measured, what...
  8. N

    Measurement disturbance - double slit

    When electrons are passed through a double slit and can either display a wave-like interference pattern or a particle-like build-up pattern, is that because their momentum/direction is changed by the measuring device interacting with them, or due to some other feature associated with being...
  9. T

    Confirming Einstein's Theory: Measurement of Bending of Light

    I just watched a show on Einstein concerning this theory of general relativity. Around 1922 photographs of stars from an eclipse were used to measure the bending of light from those stars around the gravitational field of the sun. Those measurements were used to confirm Einstein's theory. All...
  10. S

    The measurement of current in electrical appliance

    As we all know, the current should be measured in series with the multimeter... However, how do we connect the multimeter in series with home appliance without damaging the wire(plug)??
  11. I

    Particle Size Distribution Measurement

    I am interested in how PSD (particle size distribution) affects the transmittance of a material and I am trying to find an accurate process to measure it so that I can test and gather data on how it affects it. I don't know if transmittance is the proper word for what i want to study, but all...
  12. D

    Bell Measurement on 3-qubit GHZ state?

    How do you do a Bell measurement on a state that doesn't have a power of 2 number of qubits? I've got GHZ states like this: |GHZ_{ijk}> = \frac{|0_{i}0_{j}0_{k}> + |1_{i}1_{j}1_{k}>}{\sqrt{2}} And I'm trying to Bell measure the following state at qubits 2 and 3...
  13. T

    Among six measurement of the boiling point of a silicon compound,

    Question: Among six measurement of the boiling point of a silicon compound, the size of the error was 0.07,0.03,0.14,0.08 and 0.03 degree Celsius. Assuming that these data can be looked upon as a random sample from the population given by f(x;\theta) = 2(\theta-x)/\theta for 0<x<\theta =0...
  14. B

    Empirical measurement of the expansion of the universe

    Doppler shift of light shows distant galaxies moving away from us at high speed. This of course has been taken to prove that the universe itself is expanding and it has been theorized that the expansion is accelerating. To actually empirically measure and prove the theorized acceleration...
  15. L

    Heisenberg photons and particle velocity measurement

    Hi, [c=speed of light] if a particle travels at a velocity x/t and momentum p, such that (c-x/t) < (delta-x)*(delta-p) (ie the Heisenberg limit), how could one tell whether what one was looking at was a photon traveling at speed c or a particle traveling indeterminately CLOSE to c? also...
  16. Peeter

    Hydrogen atom. state after L_z measurement

    Homework Statement An initial state is given: {\lvert {\psi(0)} \rangle} = \frac{1}{{\sqrt{3}}} \left( {\lvert {100} \rangle} + {\lvert {210} \rangle} + {\lvert {211} \rangle}\right) An L_z measurement is performed with outcome 0 at time t_0. What is the appropriate form for the ket...
  17. H

    Solve Quantum Measurement Homework: Wavefunction After q1 Measurement

    Homework Statement For a particle in an isolated system, the Hamiltonian operator has normalised eigenstates and eigenvalues u_{n}(x) and E_{n}, respectively. The operator of another variable Q has normalised eigenstates and eigenvalues \phi_{n} and q_{n}, respectively. The lowest two Q...
  18. S

    Can a circuit output a voltage proportional to frequency of a square wave?

    Hi, Im am building a measurement device to measure the speed of a fan. Essentially I have a diode on one side of the fan, and a phototransistor pointing to it on the other side of the fan. This results in an output signal resembling a square wave. I am also trying to build an circuit...
  19. Q

    What constitutes as a measurement?

    I was talking to my professor about what constitutes as a measurement and the topic of the Stern-Gerlach experiment arised. *Please don't discuss about schrodinger's cat and that funny business, I've heard it many times and I am very bored of that discussion. Please no metaphysics BS, I want...
  20. G

    Actual earth measurement contradicts measurement predicted by special relativity

    A particular muon lives to the ripe old age of 4.5 microseconds (three half lives). As it sits in its chair, ticking off the picoseconds, it observes the Earth streaking by at 99.99999995% light speed. What will be the elapsed time of the muon's life, as measured on the Earth clock? As I...
  21. V

    Differential Pressure measurement problem

    Here is a relatively simple problem. I'm wondering if someone can give me their opinion on it or actually know experimentally if it is true. Here is the diagram: A flow of liquid (say water) is pumped through a pipe that has a reduction in diameter. You place a pressure gauge before...
  22. C

    Measurement in de broglie-bohm theory

    Hi, Could you describe the "before the measurement" mechanism in de broglie bohm theory? Is there a real collapse during the measurement? Can we determine the particle's position in its guiding function without disturbing it? Is there any way to calculate guiding function?
  23. S

    Proposal for measurement of Lens Thirring effect

    I don't possesses enough knowledge of GR to know if this proposal is feasible (or even remotely possible) I would welcome any constructive criticism of the following idea for detecting Lens Thirring effect: Apparatus consists of a dense, massive sphere or disc, rotating at high velocity...
  24. O

    Descriptive Statistics - Find % of measurement in a certain range

    1. The problem statement: A set of measurements of a parameter x has a normal distribution with mean of 50 and standard deviation of 1. If there are a very large number of measurements, approximately what percentage of measurements would you expect to be in the range 48 < x < 50...
  25. G

    Conversion of emu measurement to Tesla

    Homework Statement I took a Moment vs field measurement of magnetic thin film taken on a VSM. The Bs of the material is given in emus. I want to convert this to a moment value in Tesla as it is typically given in publications. Are VSM measurements actually emu/cm3 despite being given as...
  26. M

    Understanding Reactive Power Measurement with Wattmeter Configuration

    Does anybody understand how this wattmeter configuration is measuring reactive power? Thanks
  27. Dimani4

    Is my device's capacitance or resistance causing a measurement problem?

    I did some device that should be capacitor. when i try to measure capacitance I got some capacitance that varies like that:(1.5-2.5nF), but.. then i wanted to check resistance just for curiosity.. I got some result..it shows me 1.34MOhm. How it could be? As I understand it should be or...
  28. S

    Measurement of two components of electron spin

    Quantum physics texts describe how it is impossible to measure S(z) and S(x) spin components of a single electron at the same time where z represents the z axis,etc. What would happen if you try to trick nature by using a correlated pair of electons, emitted from an ion, moving in opposite...
  29. C

    Fundamental Measurement of Subatomic Particles: Techniques and References

    I am curious how exactly fundamental measurements are made for subatomic particles. I am hoping someone who knows can point me to some references as to the following: 1) How is the position of a photon measured? 2) How is the position of a subatomic particle measured? 3) How is the momentum...
  30. R

    IQ is supposed to be the measurement of your natural intelligence.

    IQ is supposed to be the measurement of your "natural intelligence." IQ is supposed to be the measurement of your "natural intelligence." However, can your IQ vary on how much brain activity you're doing? For instance, during the Summer a person is lazy and not doing any studying or anything...
  31. A

    How do you count Uncertainty Measurement using Precision Error and Bias Error?

    Homework Statement Find the Uncertainty Measurement using Precision Error and Bias Error? The Length of line is 5.625 in. Precision Error is 0.13 in. Bias Error is -0.115 in. What is the UNCERTAINTY measurement? Homework Equations None. The Attempt at a Solution Please help! I...
  32. L

    What is an observation or measurement?

    What is an observation or measurement? If it is not known exactly I would like to at least have some good appreciation of what the fuzzyness of the boundary is.
  33. nukeman

    Quick angular measurement question about moon. Thanks

    **Quick angular measurement question about moon. Thanks! I am suppose to write a calculation on finding angular measurement of the moon. Does the following make sense, and is correct?
  34. R

    Collapsing a wave function by measurement

    Lets say we have a system in a 1D infinite potential well, prepared somehow with the wavefunction: (phi)=C(a-x)x. I understand that if I try to measure the system's energy, I will collapse the system to an eigen state ((psi)=Asin(n pi x/length)+Bcos(n pi x/length)), returning an eigen energy...
  35. J

    Save me automatic measurement system for solar panel

    [b]1.I need to create an electronic system that automatically can measure and derive the IV and I-P characteristics (graph) and it must show maximum power point on the graphs. [b]2.The system must include a homemade voltage controlled electronic load that can load the solar cell with a well...
  36. T

    'New' type of angle measurement to often replace radians

    Maybe I'm biased because of the kind of projects I'm pursuing (raytracing), but I can't help feeling that for many areas, instead of defining a circle in terms of radians (or degrees for that matter), we should simply use unity and define say, a quarter of a circle as being 0.25. Obviously a...
  37. M

    Double slit measurement problem

    In the two slit experiment there is an interference pattern generated whenever there are no detectors at the slits. This must mean that the wavefunction associated with the particles have not decohered. But the wavefunction must have interacted in some way with the barrier in order to produce...
  38. Helios

    Ecliptic Longitude Measurement

    I have an idea how to measure the ecliptic longitude with a sundial type device. Ecliptic longitude is a astronomical variable so I chose this forum. Suppose we have a verticle flag pole poised on the equator of the Earth. A "coordinate circle" is drawn that surrounds the flag pole, radius =...
  39. K

    Radium 226 Dangers & Measurement: Facts & Safety Tips

    Hi, i have a question about the radioactive behaviour of radium 226 and its dangers. The reason for my question is that I'm going to work in a town, where unfortunately the beach is polluted with radium 226. I'm concernced about this issue and want to know how dangerous this has to be...
  40. M

    Measurement Problem: Wavefunction Interaction with Macroscopic Objects

    Is it correct to say that a measurement occurs whenever a wavefunction interacts with a macroscopic object? If this is the case why does the wavefunction make a distinction between a photon detector and say a half silvered mirror used in quantum experiments. Both are macroscopic objects but in...
  41. I

    Distance measurement by means of optical interferometry

    Hi, I have been assigned to a new task in my job where I have to investigate on measuring the distance to an object by means of optical interferometry (Michelson interferometry). I have been looking for info on the subject but have not been really lucky. I have been able to obtain the...
  42. N

    Ultrasonic in distance measurement

    Hi tehre, this is my firs post here! I'm designing a complex system using a 40kHz ultrasonic transducers in distance measurement for waste container level detection. Now I have a big problem because the hot season change the air properties in temperature and humidity. Anyone may help me...
  43. Philosophaie

    Where are the starting points for measuring celestial coordinates?

    Where is the starting point of measurement of the Ecliptic Longitude, the Ecliptic Latitude, Right Ascension, and Declination?
  44. zonde

    Commutativity of frequency measurement

    Let's say we have photon beam with certain frequency. Now we make a choice to perform one of two noncomuting measurements, say polarization measurement in H/V basis or polarization measurement in +45°/-45° basis. After that measurement we perform frequency measurement. From QM perspective it is...
  45. G

    Magnetic susceptibility measurement

    Hi, I have to make a coil.I do not know anything about its dimensions but know that it is to be used to measure magnetic field,its actually to be used in a magnetic susceptibility measurement.There are 3 coils, drive, excitation, measurement and I/p is given at 1000hz frequency. I need to...
  46. S

    Is the constant c (or it's measurement) subject to the uncertainty principle?

    I appologize if my questions make no sense (very likely as I do not have a physics background). 1. The uncertainty principle states that precision of measurement is identified only down to the Planck's constant. If this is so, how can one measure the speed of light with infinite precision? ANd...
  47. R

    Measuring Particle Velocity of Sound in Water

    I have to measure the particle velocity of sound waves in water. Which instrument to use to measure particle velocity of a sound in a specific direction. I searched but I find some anemometer setups for velocity measurements. I think they are all water flow measurement methods. Is there any...
  48. D

    Measurement problem -basic definition.

    is this a correct way to describe the MP? It means that everything is everywhere doing everything in every possible state at all times, until something conscious looks at it, then, as a result of the observer, it takes a state, which is only subject to how the observer perceives it. We only...
  49. S

    MATLAB Solving a Matlab Radiation Measurement Loop Over a Year

    I have a code in Matlab where I need to measure the radiation on a specific latitude over a year. I have my time steps in hours and I am iterating over a year. I have parameters for the amount of radiation per hour in a 24 hour period, but my problem is that I want to loop this 24 iteration loop...
  50. W

    Wavefunction collapse and measurement

    So, rookie question, I know, but I'm having a little trouble with the idea of wavefunction collapse as it pertains to stationary states: If a measurement of energy collapses a wavefunction into an energy eigenstate, it stays there forever (unless perturbed). But my impression is that although...
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