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# Questions tagged [data-analysis]

Use for question relating the the techniques of data analysis.

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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 ...
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?
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 ...
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: ...
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" ...
118 views

### What causes the 20 second period in LIGO data?

I download LIGO data on GW150914 (gravitational waves) via the code in Mathematica ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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)
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....
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 ...
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 ...
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 $y$-...
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 (...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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?
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 ...
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). ...
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 ...
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 ...
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$\sigma$". ...
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 ...
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 ...
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 ...
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 $\theta$ (...
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. ...
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. ...
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 ...
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 ...
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 ?
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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.
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?
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?