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Questions tagged [data-analysis]

Use for question relating the the techniques of data analysis.

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1answer
58 views

Determining Threshold Voltage and Plateau from experimental data

I’ve been trying to figure out how to interpret the following data from the Geiger muller tube There are only seven data points. Where does the plateau begin? Has the data collection begun after the ...
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1answer
41 views

Tracking efficiency for experiments at CERN

For various experiments (e.g. ALICE, CMS etc) at the CERN-LHC, people talk about tracking efficiency. What exactly is this tracking efficiency? How different is it from reconstruction efficiency?
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1answer
98 views

Convergence tests for experimental data

I ran a simulation for the critical density at which traffic flow transitions from laminar flow to start-stop-waves. The results for different road lengths are: From the graph we can see that the ...
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0answers
43 views

Question about statement of uncertainty

I have a doubt about uncertainty of a measurement. I have a sample of a specific material which is my reference material and it is calibrated and NIST traceable. This sentence is in its data-sheet: ...
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0answers
68 views

What are common methods to remove discretization on experimental measures?

I have some experimental data, and since the measurements are digital, the data is discretized/quantized/rounded/truncated. I need to know if there are general methods, or common methods, to "smooth" ...
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1answer
118 views

What causes the 20 second period in LIGO data?

I download LIGO data on GW150914 (gravitational waves) via the code in Mathematica ...
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0answers
1k views

Parallel Axis Theorem Experiment

I am currently working on a physics experiment to confirm the parallel axis theorem. To do this, I have the following setup: In this experiment I change the distance between the centre of the ...
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1answer
751 views

Moment of Inertia and Mass Experiement

I am currently working on a physics project to experimentally confirm the relationship between mass and moment of inertia. The experiment is setup as depicted: In this experiment, $r1$ and $r2$ are ...
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0answers
49 views

Correlations and associativity

Suppose one has a set of data $D$ and a theoretical model $M(A,B,C)$ one wants to fit to it by obtaining the best fitting values of the parameters $A,B,C$, which in principle are free. Plotting the ...
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1answer
28 views

How to find average in this case?

If we have 10 trials of measuring density each repeated three times. How can we find average? Do we take the average of each trial and then find the average of the averages? Would this be physically ...
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0answers
64 views

Uncertainty of interpolation when covariance matrix is given

Assume that there is a given covariance matrix of an evaluated quantity ( in my case it's a rection cross section $\sigma = f(E)$, where $\sigma$ is the cross section and $E$ is each energy point ...
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3answers
956 views

Uncertainty in counting population? Vs uncertainty in measuring length?

I know that when I use a ruler to measure the length of a table, an uncertainty will be the finite width of the ruler's markings. What about when counting people? Say I count the number of people ...
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2answers
82 views

Consistency of data

In particle physics, what factors do we consider to conclude that the measurements done by two different experiments are consistent with each other? (You may even explain the concept with an example)
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2answers
70 views

Experiment on friction coefficient

Here you can see the results of the experiment about a friction coefficient: The mean of the friction coefficient becomes 0.262 but when I do a linear regression in the form of y=mx the slope is 0.31....
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2answers
176 views

How to analyse gamma ray spectra?

I have recently done an experiment using gamma radiation and am now at a loss as to how to analyse the data I acquired. I have a background spectrum and a spectrum from a radioactive sample and need ...
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0answers
49 views

Can a particle be identified when one knows $\left<dE/dx\right>$ and the Cherenkov angle $\theta_c$?

I have a question about if it would be possible to identify a particle by measuring the energy loss due to ionization $\langle dE/dx\rangle$ and the Cherenkov angle $\theta_c$. I assume that we know ...
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2answers
62 views

How does finding the $y$-intercept of a graph reduce error compared to finding the average of the data set?

In my particular case I have the equation $$ \frac{1}{d_i} = -\frac{1}{d_o}+\frac{1}{f} $$ and I'm plotting $\frac{1}{d_i}$ against $\frac{1}{d_o}$ to give an intercept of (in theory) -1 and a $y$-...
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1answer
88 views

Difference between Fourier and Laplace transforms in analyzing data

I have a set of displacement-time graphs from an experiment to convert to the frequency domain. Both the Fourier and Laplace transform seem to do this, so what's the difference between them (...
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0answers
68 views

What “error” should we report? The standard deviation of the mean or twice the standard deviation of a single measurement?

According to some sources, when one performs $N$ independent measurements of a Gaussian-like distributed values, one should report the mean value $\pm \text{the uncertainty}$ where the uncertainty is ...
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2answers
178 views

Reporting an uncertainty lower than the precision of the apparatus?

When performing $N$ independent measurements following a Gaussian distribution, it is sometimes said to report the mean and the standard deviation of the mean as value and its uncertainty. Now, the ...
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1answer
355 views

When to round off standard deviations in uncertainty propagation?

Let's take a concrete example. One is dealing with a wire through which a DC is running. One measures its voltage and obtain its current by measuring the magnetic field around it in some way such that ...
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1answer
303 views

What do we mean by fit of data in particle physics?

I am unable to clearly understand the meaning of fitting the data. Like in this paper of determination of mass and width of Z boson and number of neutrinos (from ALEPH detector) Does it mean that ...
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1answer
38 views

Reason for borexino pep flux confidence level error

At the TAUP conference in 2011, the Borexino collaboration presented an analysis of electron-neutrino elastic scattering events in their liquid scintillation detector to claim the first observation of ...
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1answer
254 views

Determination of spring constant $k$ for an elastomer

Primary Question: How can you determine the spring constant $k$ of an elastic material? I was recently tasked with finding the spring constant for a series of elastomeric materials, the first of ...
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1answer
356 views

Analyzing the rates of cooling points using the graph and data [closed]

how should i use this data to analyse the differences between the two materials. and what calculations could i use for it?
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1answer
199 views

What is the difference between data-driven and semi-data-driven techniques?

I keep hearing the terms data-driven and semi-data-driven techniques(especially for background estimation) in many CERN analysis talks. I looked for their difference but didn't find any documentation ...
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1answer
452 views

How to estimate the goodness of a 2D fit using the chi-square distribution?

I have measured a quantity $b$ as a function of two variables, let's say $x$ and $y$. Then I fitted a 2D polynomial of the shape $$b(x,y) = \sum c_{j,i} x^i y^j$$ to the data (which is of 2nd order). ...
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1answer
308 views

What is meant by “decay topology” in experimental high energy physics

Often we come across 'decay topology' while doing data analysis in experimental particle physics. My guess is that it represents decay of a particle and how it decays and into what it decays. Edit: I ...
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3answers
83 views

Describe the dynamics of a fluctuating vector

I have a time series for the $\mathbf{v}(t) = (x,y,z)$ components of a vector quantity. It is fluctuating in time, and has a non-trivial autocorrelation function which I want to somehow elucidate. The ...
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1answer
132 views

Question when comparing two experimental results

In my textbook it says that if two experimental results vary less than 3$\sigma$ then they can be considered to have arrived at the same result. My question is how do you determine this "x$\sigma$". ...
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1answer
57 views

What is the actual significance of increasing efficiency of a detector?

Say, I have a gamma detector with a 80% detection efficiency. And I buy a new one, with 85% efficiency, or even 90%. How exactly does it benefit me to be having 10% greater efficiency, other than to ...
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0answers
39 views

Is there a mathematical model that models spectral power distribution curves?

The experiment was aimed to find the specturm cruve of different light bulbs experimentally. Is there a mathematical way to justify the results I obtained (the plotted graph)? Would the equation in ...
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1answer
48 views

Is it valid to compare experimental data and theoretical data like this? Does the vertical axis of the graphs have to correspond?

The plotted curve is the experimental value of the SPD curve. Though it doesn't look "spikey" as it should, stacking the image on top seems to explain that the data is infact correct, but that more ...
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0answers
118 views

Calculation of mixing angle and mass squared difference in neutrino experiments

How is an exclusion curve/contour plotted in $\Delta{m^2}$ - $\tan(\theta)$ plane from a given experimental data and how the best fit value of $\Delta{m^2}$ (mass squared difference) and $\theta$ (...
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5answers
3k views

How do scientists determine when to disregard a model that has a higher correlation to data than another model?

For any set of data points, you can comprise a 100% correlated and fitted curve using a sum of sloped lines all multiplied by their respective Heaviside step functions to form a zig-zag shaped curve. ...
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1answer
1k views

What are signal efficiency and background rejection?

Recently I came across the terms signal efficiency and background rejection (for example in this paper), but I couldn't find an understandable definitions to those terms and how they are used. ...
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1answer
106 views

Selection criteria in experimental particle physics

I often read in particle physics articles, "relaxed selection criteria" and "nominal selection criteria" of events. what is the meaning of relaxed and nominal ? PS : Links and details would be ...
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1answer
134 views

Data driven and MC simulated background in experimental particle physics

In experimental particle physics, we use for data analysis a set of samples to simulate the background and the signal we want to observe. When reading articles, I often encounter a section dedicated ...
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2answers
374 views

What does vertical axis labeled “events/energy” mean in histogram?

What does vertical axis labeled "events/energy" mean in histogram? Why is events divided by energy 0.1 GeV ? Why is events divided by energy 0.5 GeV ?
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0answers
162 views

What does it mean if there's no peaks on raman spectrum?

I carried out Raman measurements of a doped semiconductor. I know what are the peaks of undoped one. I also know, that usually doped semiconductor has at least few peaks in similar positions to the ...
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2answers
581 views

Why do we plot distributions (histograms, etc) per logarithmic interval (i.e. per “dec”/“dex”)?

I was trying to explain why we plot distributions (for example the Luminosity distribution function attached) per logarithmic interval (another example would be spectral energy distributions per ...
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1answer
215 views

How are Raw Observations Processed to Obtain Pure CMB Data?

I'm confused about how they identify and subtract radiation from unwanted astronomical sources while measuring the Cosmic Microwave Background Radiation. Here's what I initially guessed: The dipole ...
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1answer
237 views

Comparison between Bethe-Weizsäcker-Model for the nuclear binding energy and measurements

I tried to compare the binding energies of between the measured data and the Bethe-Weizsäcker model. My plot looks like this and I don't understand the large discrepancy: For the measurement I used ...
3
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1answer
330 views

How to deal with outliers in experimental physics?

In experimental physics, is it generally considered a good practice to eliminate outliers? I was taught that, when doing a linear regression, I should prune all the data that doesn't fit within 3 ...
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2answers
40 views

In astrophysics, why is it OK to compare one observed galaxy field with the average of multiple simulated fields?

I am currently doing my BSc project on weak gravitational lensing. My supervisor gave me data from a field of galaxy clusters observed by the CFHTLenS. She also gave me the data of 64 simulated ...
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1answer
394 views

Interpretation of invariant mass distribution plots

Can someone explain what exactly a invariant mass distribuition is and how to interpret the follwing graph. Especially what Events/GeV means.
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1answer
665 views

What exactly is background in terms of data analysis in particle physics? [closed]

I often come across the term "background" in particle physics. Could someone explain what it exactly means?
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2answers
338 views

What does “applying a cut” mean in terms of particle physics?

I often came across the phrase "to apply a cut" in terms of data analysis in context of particle physics. Could someone explain what it means?
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0answers
64 views

Interpretation of TGA-DSC data in terms of composition of iron oxides

I have thermogravimetric (TGA) and differential scanning calorimetry (DSA) data for an iron (hyd)oxide sample and I would like to interpret this data in terms of the composition of the starting ...
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2answers
508 views

How to deduce the charge of an electron from the charge of an oil drop in the Millikan experiment?

In the Millikan experiment we measure the charge of one oil drop. But how can I measure charge of one electron when I’m not sure how many electrons are contained within one oil drop?