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Questions tagged [error-analysis]

Techniques and methods for computing, estimating, or placing bounds on the errors of expressions (formulas) based on knowledge of error distributions, error intervals or bounds of variables and parameters entering those expressions, and of methods used in the computations.

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116 views

A theoretical limit of accuracy?

Is there an agreed upon/conjectured theoretical limit to our ability to resolve the accuracy of time?
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1answer
20 views

Length and velocity of a pulse of particles

We are given a pulse of protons of duration $10^{-7}s$ and energy $2KeV$. I know I am supposed to use the uncertainty principle to solve this. I need to get the length and the indetermination of the ...
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1answer
29 views

Least count of Vernier

Is least count not always 1 main scale divsion-1vernier scale divsion or is it always least reading possible on main scale/ no of vernier divsions. question: 1 main scale reading be 1 mm Lets say 5 ...
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1answer
25 views

The difference in using a predetermined error or standard deviation for calculations

Please edit the thread's tags and content if there are mistakes. I am not sure where If I'm posting my question with the right tags. This is a simple question regarding the study of Linear Motion by ...
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2answers
45 views

What is the proper way to combine two different errors for the same measurement?

We did an experiment in the lab (regarding magnetic domain walls) that yielded some pictures that we later on analyzed and manipulated in Matlab (we took an RGB image made it into grayscale one and ...
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0answers
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Why -20dB is taken as the standard rejection ratio for optical mode rejection in multimode waveguide?

In case of multimode waveguide to demonstrate perfect mode rejection, I saw researchers use boundary of -20dB. If mode power at output is less then -20dB, it is considered as fully rejected/filter out....
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1answer
37 views

Error propagation and data linearization

I am fairly new to teaching error propagation to students but came across a question I couldn’t answer myself. Say we have a set of data that produces a parabola. In order to linearize the data and ...
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1answer
25 views

Intuition behind swapping the known and unknown resistance in a slide wire meter bridge

Today I was learning about wheatstones and balanced meter bridges. But while learning about the sources of error while working with the meter bridge (measuring unknown resistance), I couldn't ...
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2answers
58 views

When is the order of magnitude not equal to the exponent of scientific notation?

Explain why the order of magnitude is sometimes not the same as the exponent in scientific notation. It is because of the units?
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2answers
28 views

Would equipment that is wrongly used by a person be considered as a systematic error?

Would equipment that is wrongly used by a person be considered as a systematic error or a random or both? I would say a systematic error because a person could don't know how to use a ruler and starts ...
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0answers
54 views

Relativistic vs. non-relativistic Error

I want to clarify a concept for myself. Is it correct to use the following formula for finding the error in measured relativistic momentum and non-relativistic momentum: $$\frac {\gamma mv-mv}{\gamma ...
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0answers
25 views

How can I determine, in what extent the fit to experimental data is good in Matlab?

I have experimental spectrum in which y-axis is intensity values, and x-axis is frequency values. Int - array of experimental intensities (y-axis). w - array of frequencies (x-axis). I know the view ...
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2answers
845 views

Significant figures while finding errors

The question which arose my confusion: Two resistors with resistance $R_1 = 100\pm 3 \ \Omega$, and $R_2 = 200\pm 4 \ \Omega$ are connected in (a) series, (b) in parallel. Find the equivalent ...
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3answers
123 views

Is this the definition of significant figures?

In a thread I posted recently about significant figures, someone said that they are defined as follows. I will use an example to save time trying to generalize the definition. The person said, for ...
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3answers
45 views

Uncertainty in ripetitive measurements

Good afternoon everyone, I have a question which is puzzling me and I did not found an acceptable answer yet. Suppose you have acquired some data from a measurement and you have the following numbers: ...
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1answer
23 views

Uncertainty estimation of a quantity after its calibration

I have to calibrate power output of a diode to its input voltage. The voltage source has negligible error but the power meter has significant uncertainty (a couple %). I take a number of power ...
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10answers
8k views

Why aren't the 0's significant figures in 0.002?

I understand that significant figures is a term used for "reliably known digits". However, what I don't understand is why the 0's are not counted among these in numbers such as 0.002. Surely, if we ...
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7answers
1k views

When to average in the lab for indirect measurements?

I am measuring distance and time to calculate the velocity. I repeat the experiment 10 times. What is better, to first calculate the average of distance and time and then the velocity, or to calculate ...
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0answers
30 views

How to fit mean squared displacement data from nanoparticle tracking analysis?

I am trying to independently analyze raw nanoparticle tracking analysis (NTA) data, but my diffusion coefficients calculated directly from x and y pixel values only moderately correlate with reported ...
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2answers
54 views

Scientific notation and usage thereof [closed]

I'm taking my first physics exam in university this Saturday, and I'm currently working on a practice exam. I got the answer 3.1MeV for a alpha-decay question, but the answer was 3100keV. I ...
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3answers
174 views

Calculating uncertainty when combining parallel resistors

A recent question asks students to calculate the total resistance of parallel resistors R1 and R2 with uncertainty. R1 = 120 Ω (+/-10%). R2 = 500 Ω (+/-10%). We would normally use the ...
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3answers
79 views

Error propagation with a pendulum

The following is a 2018 F=ma exam question. I know that this isn't a homework site, but I think that my question is conceptually relevant. Here's the problem: A group of students wish to measure ...
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2answers
55 views

How to calculate the error when multiple measurements are made, each of which has an error?

So if I have made three measurements, measuring the same physical quantity $d$: $a \pm \Delta a$ $b \pm\Delta b$ $c \pm\Delta c$ and I want to take the average of $a, b$ and $c$ to get the ...
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0answers
9 views

How to combine RTD sensor tolerance with system resolution

I have a Pt1000 resistance temperature detector (RTD) with stated tolerance --for some positive temperature t-- of 0.15+0.002*t[degC]. At the same time, the resolution of my readout system is 0.01 ...
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0answers
32 views

Teeter Totter Team Building Game

I recall doing a team building exercise where a team of about 4 people needed to balance a teeter totter, so that neither of the ends was touching the ground. They could achieve this by having the ...
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1answer
59 views

Propagation of asymmetric error bars [duplicate]

I have two (fully independent) measurements of the same quantity X. Each of them reports a measurement $X_{\sigma_L}^{\sigma_R}$, where $\sigma_L$ and $\sigma_R$ are the left and right uncertainties (...
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1answer
27 views

Background illumination and noise/Double slit experiment

I have obtained a value for the background illumination with an associated error which was kept constant during a double slit experiment. Also, I have acquired a value for the average noise/...
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1answer
41 views

What's the number of significant digits for error bars? [duplicate]

What's the number of significant digits for error bars? For example, the Particle Data Group lists the proton mass as, $$938.2720813 \pm 0.000058$$ Should I take $0.000058$ as having 2 significant ...
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2answers
89 views

Notation in Heisenberg Uncertainty Relation: greater than with tilde: $\gtrsim$

In "The Road to Reality" (pg. 523), Roger Penrose writes: Heisenberg's uncertainty relation tells us that the product of these spreads cannot be smaller than the order of Planck's constant, and ...
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2answers
55 views

What does a double parenthesis in a quoted value ─ like e.g. 157(3)(3) ─ mean?

Sometimes, in journal articles, the author writes a number followed by two parenthesis. For example, $157(3)(3)$, where it seems that the first parenthesis shows uncertainty in the last digit (here, $...
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1answer
31 views

How do I determine the accuracy of this two-dimensional potential field?

Let's say I want to solve this problem. I know the values on the boundaries and I guess an initial solution on the rectangular grid inside these boundaries, see figure below. Potential=10 on ...
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1answer
47 views

Shorthand error notation (with brackets) accros decimal point

I have a small doubt regarding the use of shorthand error notation, i.e. $6.626070150(81)$ instead of $6.626070150 \pm 0.000000081$. When the error has 2 s.f. (such as when the error is just over $1 \...
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1answer
49 views

What is the error propagation in an FFT (Fast Fourier Transform)?

I use an insert FFT graph feature on a program called logger pro. If I have the uncertainty of my input data, can I know what the uncertainty of the FFT computation will be?
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2answers
55 views

Relation between momentum and momentum uncertainty

I have read the following sentence in a section which is explaining why particle accelerators need such high energy: As we require high precision position measurement, the Heisenberg uncertainty ...
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2answers
879 views

Uncertainties in Logarithms

I have plotted data of temperature against time for a cooling cup of coffee and gotten a nice curve. I have then linearised this data by taking the log of the temperature for the purposes of gatting a ...
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3answers
64 views

Is it possible to suggest a physical experiment in which measurement errors are dramatically increasing? (due to the accumulation of errors)

Is it possible to suggest a physical experiment in which measurement errors are dramatically increasing? (due to the accumulation of errors) Maybe some magnetic field can be used here? Or any other ...
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1answer
22 views

how to estimate the error of FTIR spectra?

how to estimate the error of FTIR spectra in transmission, especially on the wavenumber ? please
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1answer
24 views

Propagation of uncertainty for a mean value

During an experiment I had to measure the speed of light $c$ (it's an indirect measurement, because i had $c(x,y,z)$ as a function of some quantities $x,y,z$ I could measure). I took several measures $...
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1answer
70 views

Problem in measuring uncertainty

While performing an experiment involving a bar pendulum, we had to measure the time period of one oscillation by measuring the time taken for 30 oscillations. There is some confusion regarding ...
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1answer
273 views

Propagation of uncertainties while calculating trigonometric ratios

If one has an equation such as $$x=-(3.2±0.1)\cos(30.3º±0.2º).$$ How does the error carry to be able to find the value of $x$? I have found that you have to -sine the error in the cosine, but then how ...
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1answer
22 views

Error of capacitnace measurement using a multimeter

physics stack exchange Many multimeters have a setting for measuring capacitance. The multimeter I have has a precision of four significant figures, or in other words, it returns the value in the ...
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1answer
116 views

What will be the uncertainty in $\mu_0$ under the new SI scheme?

As you may be aware, a new SI system is likely to be adopted in November 2018 (see https://www.nist.gov/si-redefinition/kilogram-introduction). Whilst the speed of light remains a fixed quantity and ...
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1answer
87 views

Uncertainty Principle - Accuracy or Precision? [closed]

While discussing about the Uncertainty Principle, some books use the word 'accuracy' and some other books use the word 'precision'. Some even use them both interchangeably. For instance, in Griffiths' ...
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0answers
45 views

What is the uncertainty on 50 Hz a.c.?

We are doing an experiment to measure velocity using the ticker-tape timer which runs on a 50 Hz a.c. 12 V power supply. I am in Ireland. So the time interval between each pair of dots is 0.02 s. But ...
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2answers
96 views

Formula for combining relative uncertainties [duplicate]

Different sources are giving me different formulae for combining relative uncertainties. One tells me to simply add the relative uncertainties together to get the combined uncertainty while another ...
2
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1answer
42 views

Experimental results of Higgs Boson

In 2012, ATLAS and CMS posted results of the mass of the Higgs boson, $126.0 \pm 0.4$ (stat) $\pm 0.4$ (sys) $\ \mathrm{GeV}/c^2$ and $125.3 \pm 0.4$ (stat) $\pm 0.5$ (sys) $\mathrm{GeV}/c^2$. What ...
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6answers
1k views

Are uncertainties higher than measured values realistic?

Whenever I measure a positive quantity (e.g. a volume) there is some uncertainty related to the measurement. The uncertainty will usually be quite low, e.g. lower than 10%, depending on the equipment. ...
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1answer
52 views

Measuring uncertainty in measurements

The following question is taken from Physics by Halliday, Resnick and Krane, 5th ed. Vol. 1. A student is calculating the thickness of a single sheet of paper. She measures the thickness of a stack ...
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1answer
47 views

Imprecision in experiments

When dealing with breadboards, and electronic circuits in general, in my case finding the total (equivalent) resistance using an ohmmeter, what are the factors that make the experimental value not ...
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1answer
60 views

Uncertainty cannot be calculated?

I'm doing an experiment on resonance. The phase difference between the driving force and the one oscillating is given by $$\varphi=\arcsin\left(\frac{y_1}{y_2}\right)$$ where $y_1$ and $y_2$ are ...