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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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40 views

Sig Figs in Coulomb's Law [on hold]

Because Coulomb's constant only has 1 sig fig, should all of my answers have 1 sig fig when doing a problem with Coulomb's Law?
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2answers
47 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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0answers
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Should these two graphs be plotted together (each with an axis 1/3rd length of the other) [closed]

I am writing a lab report, and have been recommended that I should plot lines on the same graph to save space. These distances are different due to different samples being used. The issue I have is if ...
2
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3answers
61 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
51 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 ...
1
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2answers
47 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
18 views

Best method for determining tolerances based on production data [migrated]

Say I am producing a wound coil which is ultimately going to be used in a colpitt's oscillator circuit. I measure the Ls and Rs of the coil, and then install it in a ferrite and then test it in the ...
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0answers
7 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
28 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 ...
3
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1answer
45 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
25 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
33 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
86 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 ...
2
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2answers
50 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
30 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
28 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 \...
0
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1answer
39 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?
2
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2answers
50 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 ...
7
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2answers
745 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 ...
2
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3answers
61 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
20 views

how to estimate the error of FTIR spectra?

how to estimate the error of FTIR spectra in transmission, especially on the wavenumber ? please
2
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1answer
22 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
65 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
251 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
18 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
105 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
77 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
33 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 ...
2
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2answers
68 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
votes
1answer
39 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
42 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 ...
2
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1answer
55 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 ...
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1answer
33 views

Significant figures in multiplication with units

Why does it make sense to round to the smallest significant figure instead to the largest unit? If I have one measurement made to the nearest millimetre and another to the nearest picometre then why ...
2
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0answers
43 views

Uncertainty calculation - when to use absolute value bars?

I'm asking this because I saw (at least) two questions here on this Stack that seemed very similar and caused the same confusion to me in reading the answers to both. Suppose we have a formula: $A = ...
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3answers
49 views

Confusion with regards to uncertainty calculations

Let’s say we have a scenario of a ball being released from the top of the building. This can be modeled simply with the kinematics equation $S=ut +\frac{1}{2}at^2$, which reduced to $S=\frac{1}{2}at^...
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3answers
62 views

Uncertainty when multiplying two measured values

Until now I have been using this rule: "The result of the multiplication or division must not have more significant figures than the operands." when dealing with uncertainty in multiplification....
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1answer
69 views

Why does taking more readings reduce random error? [closed]

So I was tossing a coin And I did two experiments Experiment 1: Tossing same Coin with no fan with different torque each time and did'nt much care about orientation of the coin, 8 times I got 5 ...
1
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1answer
59 views

Misconception in difference between Accuracy and precision?

I know that The more systematic errors > the less accurate The more random errors > the less precise So lets say we have a stopwatch which has a zero error -1 (every ...
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1answer
84 views

Relative multiplicative vs. absolute additive error propagation

I am using the physics Cambridge book (Tsokos, K. (2014). Physics for the IB Diploma. 6th ed. Cambridge University Press.) for the International Baccalaureate and I noticed the following: When it ...
0
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3answers
52 views

Error estimation during measurements with high standard deviation

I want to measure average distance between fixed metal construction and water, as shown in the picture below to predict water flood. Let's call this distance water level h. If the water level starts ...
0
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1answer
41 views

Uncertainties in measurements and slopes

Suppose I have a mathematical model $y=mx$ and I have data for $x$ and $y$ and I want to fit the mathematical model on the data and determine the value of slope. I also have uncertainties of $x$ and $...
0
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1answer
48 views

Uncertainity calculation [closed]

The length ($l$) and width ($w$) of a rectangle is ($15.6\pm 0.1$) cm and ($10.80\pm 0.01$) cm respectively. Calculate the area and uncertainity. Solving: $$\text{Area}=15.6\times 10.80$$ $$\text{...
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3answers
197 views

Is the speed of light in vacuum $3\times 10^8\ \rm m/s$?

I saw another question which says the speed of light is "$3\times 10^8 \:\rm m/s$", and I know that the speed of light is $299,792,458\ \rm m/s$. My chemistry teacher taught me that $3.0$ means $3.0 \...
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0answers
31 views

Data-analysis (Uncertainty and errors)

This is just a data anlysis question but I thought you might need an introduction. In order to calibrate de Michelson interferometer one needs to find $\eta$ in the relation: $d = \eta D_\mu$ where $...
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0answers
22 views

Is there a more concise way to say that calculations are within the data errors of experimental measurements?

It seems that "theoretical calculations are within the data errors of experimental measurements" is a rather wordy way to express a rather simple concept, and I am wondering if there is a more concise ...
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1answer
38 views

Uncertainty when a measurement is given as “between this number and that number”

A regulation soccer field for international play is a rectangle with a length between 100 m and 110 m and a width between 64 m and 75 m. It then asked me to calculate the area which is easy but I don'...
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1answer
60 views

Precision in cosmological constant

The observed cosmological constant, what is its precision? How precise do we know is it not a fluke or misinterpretation of cosmological data?
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1answer
74 views

Significant figures in a practical experimental problem [duplicate]

Here is a question that combines uncertainties in measurements and significant figures. Consider the following results to measure the value of g: $$g={9.7,9.8,9.7,10.0,10.1,10.3}$$ Then to four ...