Questions tagged [data-analysis]

Use for question relating the the techniques of data analysis.

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3
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1answer
349 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
41 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
403 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
705 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
365 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
516 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?
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0answers
57 views

Comparing measurements from Sound Level Meters and Audio Recorders

I've been working with an environmental sound recording system that consists of a microphone -> sound level meter (SLM) -> digital audio recorder. Recently I've been involved with implementing a ...
2
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1answer
204 views

How to quantify error for a multivariate expression/equation?

Let's say I have a derived expression I want to test against experiment: $F(x,y,z)$. To do so, I have conducted the following three tests with data: Scan $F(x,y_0,z_0)$ for multiple $x$ values and ...
34
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10answers
9k views

Easy to perform quantitative experiments at home [closed]

What are some easy to perform physics experiments that can be done at home (with not too much special equipment) and that allow to actually measure/plot data and draw conclusions from it? My son is ...
1
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1answer
95 views

How to take measurements for wavelength in an experimental wave tank?

To anyone familiar to the experimental hydrodynamics field, how does one experimentally measure the wavelength of the waves generated in a plunger type wave tank or any wavetank for that matter. From ...
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0answers
40 views

Where can I find CIE 1931 RGB matching functions?

I'm unable to find CIE 1931 RGB matching functions online. Where could I find them (ideally in a tabular form with 1 nm radiometric resolution)?
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0answers
163 views

Verify standard deviation of position samples with reference

Given are the reference data samples of a moving object and data samples that are obtained from a radar sensor with corresponding standard deviations for each sample point $\sigma_t$. I would like to ...
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5answers
3k views

Is there any advantage in stacking multiple images vs a single long exposure?

Suppose I have a source object that is not time varying, to be concrete let's say it's a galaxy. Is there anything additional that can be learned or done with multiple short exposure images of exactly ...
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0answers
69 views

Looking for raw spectral data in the time domain… so I can do my own FFT analysis on it

I'm trying to get the spectral data of the periodic table of elements in the time domain format or find a site that has the data in the time domain format. All the sites I know have the data in the ...
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0answers
297 views

Na-22 Branching Ratio

I tried to calculate the branching ratio for $^{22}Na$ from experimental data using a Germanium detector. My derivation is as follows: The formula for the branching ratio $BR$ for electron capture $...
2
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1answer
54 views

Trouble with error propogation formulas for multiplication and exponentiation

In our lab notes, it states that for some relationship between variables of the form $Z=AB $, the errors are related by $$(\Delta Z /Z)^2=(\Delta A/A)^2 + (\Delta B /B)^2$$ And that for the relation ...
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1answer
214 views

Finding the combined uncertainty of weighted measurements

I am currently doing some simple simulations of radiation dose from several treatment fields. I am looking at the dose within a certain voxel of a patient receiving radiation therapy, being treated ...
0
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1answer
303 views

Convert units of Empirical Orthogonal Function (EOF) for sea surface temperature data

I have a dataset of daily averaged sea surface temperatures for an entire year. I wish to use an empirical orthogonal function to find the dominant patterns within the data. Consider that my ...
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1answer
198 views

Would a rational Bayesian agent reject String Theory as a model for particle physics?

One thing people often criticise about String Theory as a model for particle physics 1 is that it has a lot of parameters (infinitely many?), i.e. there is not just one vacuum, there is a whole ...
3
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1answer
70 views

Finding intensity/noise measurement of hysteresis loop

I'm hoping I could get some help from the experimentalists on some data analysis. I have a number of hysteresis loops taken at different angles around extinction of a polarizer on a photodiode. I ...
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1answer
139 views

What is the electron energy scale calibration?

I am reading a paper from ATLAS collaboration in CERN and it is mentioned the "electron energy scale calibration" many times. It must be related to energy calibration in the experiment but I would ...
0
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1answer
571 views

Mass Resolution- Particle's width in Particle physics?

I'm not 100% sure. but I think that the width of a particle could change depending on the decay channel. for example: The J/psi's mass resolution could be 40 MeV or in other cases 8 MeV. So I would ...
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1answer
192 views

Resources for astrostatistics

Being an astrophysic grad student with mathematical background, I have recently become interested in the field of astrostatistics. I know that this is a quite new field that combines astrophysics, ...
3
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2answers
187 views

Does a camera measure intensity? (picture of diffraction pattern on a wall)

I was performing a diffraction experiment with a slit of width 0.08mm (reported by the manufacturer). The conditions of my experiment allowed the Fraunhofer approximations. Thus, doing the Fourier ...
0
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1answer
35 views

How do low voltage differential signals transmit bits

For example: There is Din+ connected to pin a1 and Din- to pin a2. Suppose I am sending "0101". How does it get sent? If there was only Din connected to Pin a1, which has a voltage supply to the bank ...
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0answers
711 views

How to read Inverse Pole Figures (IPF) images

When (Electron BackScatter Diffraction) EBSD maps are procesed the output crystallographic orientation is derived into Euler map and three Inverse pole figures (IPF) maps. In the example there is IPF-...
2
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1answer
340 views

Simple Error Analysis for ratio of Flow Rates in a tube

I am trying to do simple error analysis but I am running into trouble. My experiment was to determine the ratio of flow rates of different pressure amounts on the tubes. My errors are: $5\%$ error ...
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1answer
431 views

How to implement Hubbert's potential to calculate permeability using Darcy's law?

Question: How does one implement Hubbert's potential to calculate permeability without making assumptions to neglect any aspects of the potential defined by Hubbert? Question's supplemental material: ...
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1answer
82 views

Sub-/Super Diffusive Processes, Time-averaged MSD and Autocorrelation. Help with interpretation?

This is a two part question, cross-posted from the Math-SE becuase I thought you people might be able to help a little more with intuition: Part 1: In a (totally fascinating) paper studying the ...
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0answers
285 views

How to plot spectral indices $n_s$ and $r$ from Planck data?

From a certain inflationary model I have obtained the theoretical values for the spectral indices $n_s$ and $r$ as functions of $N$, the e-folds number of inflation. At this point it would be ...
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2answers
347 views

Reduced chi-squared value for noiseless spectra

I am fitting synthetic spectral data. This is data in the form of a gaussian lineshape. However, although the fit looks appropriate, the value of the reduced chi-squared parameter: $$\chi^2_{\rm red} ...
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0answers
53 views

How correlated are the statistical significances of the same signal/non-signal for CMS and ATLAS?

Consider a diphoton excess for both ATLAS and CMS at the same energy for two cases: false signal: I'd expect the two statistical significances to be uncorrelated true signal: I'd expect the two ...
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1answer
180 views

How does the “Look Else Where Effect” affect the chances of detecting a false diphoton excess at the LHC?

Back in December 2015, there was found a 750 GeV diphoton excess in both CMS and ATLAS at the same location with a significance well above $3\sigma$; a 0.13% chance of being false. However, there ...
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1answer
93 views

Standard convention for $x$ error bars

What is the standard convention regarding the error bars of the independent quantity in a graph? In what situations should I show the $x$ error bars? In case both $x$ and $y$ uncertainties are ...
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1answer
2k views

How to convert intensity arbitray units to percentage in a XRD data?

In powder x ray diffraction result contains mainly two values 2theta and intensity where 2theta is in degree's and intensity is in arbitrary unit ...
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0answers
1k views

What is the difference between selection efficiency and acceptance in high energy physics?

Often in papers the product of these two quantities is mentioned, but I'm not sure what exactly they mean separately. My guess would be that one of these is the fraction of the events that you are ...
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0answers
27 views

Data Analysis: Image Sharpening through Posterization

I had this image, a picture of Jupiter: I wanted to measure the pixel diameter of Jupiter. As evident, the image is quite blurry, and thus, many value of equally justified pixel diameters can be ...
3
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3answers
792 views

What do the terms “offline” and “online” refer to in the field of high energy physics data analysis?

The title says it - I've encountered these terms several times but have never found an explanation anywhere. An example of use is this ATLAS note. If I may hazard a guess: Data rate is high at the ...
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1answer
360 views

Sloan Digital Sky Survey (SDSS) spec file headers

I downloaded spectra from Sloan Digital Sky Survey (SDSS), which has the following column headers flux, loglam, ivar, and_mask, or_mask, wdisp, sky and model (...
4
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2answers
251 views

Combining two data points with different uncertainties

I have two separate algorithms (call them "A1" and "A2") which reconstruct the $(x, y)$-position of an event in a particle detector. I can test both of these algorithms on simulated events from a very ...
0
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2answers
734 views

Least Squares Fitting - 68% Confidence Interval

I am fitting a linear polynomial to some data and I have derived the errors for each of the best-fit parameters from the covariance matrix. I would expect these errors to correspond to a $1\sigma$ 68% ...
2
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1answer
128 views

Gamma Ray Burst data

I wanted to know if there was some database for gamma ray burst (GRB) data. I would like to get the luminosity and duration of recorded GRBs. So far, I have come across this website, but since I do ...
0
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1answer
50 views

Subtracting Audio from a Song with Multiple Forms

This question may start oozing into the realm of copyright infringement, but let's discuss the theory first and foremost. I have a song with vocal and orchestral accompaniment from a well-known movie ...
3
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2answers
2k views

Best way of calculating average acceleration in lab experiments

I am doing a lab experiment that works as follows. An object moves along the $x$ axis with an initial acceleration and then moves with a pretty constant velocity that may slightly vary within $20\%$ (...
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1answer
191 views

Normalizing temperature data of CPU sensors to ambient [closed]

My scenario: I want my application to stop or take some decision based on temperature. say like if my ambient is morethan 41 i want to switch off the application and we do not have an separate ...
0
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1answer
75 views

Why is the standard deviation the error on the singular measurement?

I'm a beginner with the study in data analysis in Physics. I'm trying to understand the meaning, in the field of experimental Physics, of the standard deviation $\sigma$ of a series of data. There ...
4
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0answers
710 views

Calculating statistical significance of peak over background in counting experiment

I histogrammed the invariant masses of particular events in a counting experiment. There is a specific peak which towers over the expected exponential background. How can I give the statistical ...
1
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1answer
37 views

Should I see evidence of neutron induced gammas on a background spectrum?

If I am looking at a background gamma spectrum taken from a neutron spallation source whilst the beam was off (IE in a shutdown period), should I expect to see emissions coming from neutron induced ...
0
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2answers
32 views

Interpolating experimental data correctly (limited model knowledge)

I have data which I know follows a function $y = f(x)$ such that it is quadratic i.e. $y =\alpha x^2$ for some $\alpha$ when $x\rightarrow 0$ and $y = \beta x$ for large $x$. The data itself has ...