# Questions tagged [data-analysis]

Use for question relating the the techniques of data analysis.

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### 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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### 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 ...
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### 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 ...
549 views

### Free-Fall Lab Help - Getting weird results [closed]

So, I am doing a free-fall lab for my physics class. We got the values and I have the results here(we used a infrared photo-gate). Basically, we have a brass cylinder and a wood cylinder. Each are ...
43 views

### Searching for a textbook on Imaging

I'm hoping someone can recommend a book that will cover the physics involved in optical range image capture. I have a degree in physics, so I am looking for something on the technical end. To expand, ...
516 views

### Weighted mean from data [closed]

Suppose we have 3 experimental groups measuring "x", they measure $$x_1=\mu_1\pm \sigma_1$$ $$x_2=\mu_2\pm \sigma_2$$ $$x_3=\mu_3\pm \sigma_3$$ In the 3 experiments, we have done N measurements of ...
127 views

### What could be the distribution of an explosion energy of a mining-grade and seismic exploration explosives?

Seismic exploration involves the excitation of seismic waves using the industrially made explosive charges. What could be the distribution of explosion energy of such a charges? My guess is that it ...
36 views

### Expression for combining several probabilities in a single discriminator

I'm doing an analysis of some experiment. Details are not very important, but I've stumbled on an expression that I cannot make sense of. I have several simultaneous measurements of a certain ...
113 views

### Where can I get latest full updated list of supernovae candidates from the SDSS-II Supernova Survey?

I am doing a project where I need the list of supernovae candidates from the Sloan Digital Sky Survey II (SDSS-II) supernova survey. One list is available as part of the data-release-7 (DR7) website. ...
175 views

### Peak deconvolution [closed]

I need some help understanding how much information I can pull out of this data. I have a sample made up of two materials. Materials A and material B. Then I took a picture of the sample. The two ...
414 views

### How do I do error calculus right using gnuplot as an example?

Given is a set of measurements with their respective errors for example an energy spectrum. In gnuplot one is to fit a function $f(x;\{p_i\})$ depending on a variable $x$ and on fit parameters $p_i$. ...
98 views

### Estimate Uncertainties in Rietveld Refinement

I have the output of an x-ray diffraction experiment made on a thin film. Here I report the output of the experiment (I analyzed those data using powdercell and coloured regions have been excluded ...
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?
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### Estimate of the period of noisy “event counting” data

I have a set of experimental data, which come from a periodical event. More specifically, these are detections from a single photon detector, so there is no intensity, I only have the timestamps of ...
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### Calculating mean velocity: using time or velocity? [closed]

Background I have been running tests which involve timing an object moving a certain (fixed) distance, $s$. Each test has been repeated 3 times, and the 3 times ($t{_{1}}, t{_{2}}, t{_{3}}$) for the ...
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### Removing zero-counts in exponential decay measurement

I'm doing an experiment where I'm measuring the mean-lifetime of muons. I have a set of data points for the number of decays against time, resembling an exponential distribution (of course). But in ...
306 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 ...
313 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 ...
12k views

### Terminal velocity of a steel ball in water [closed]

I am investigating on the terminal velocity of steel balls moving in water. I used the balls with different diameters, such as 3.17mm, 6.02mm, etc. And I used a full-filled 1L graduated cylinder. I ...
66 views

### Data for binary systems

I am looking for binary systems data that can be used in the context of Kepler's laws. Masses, distances, periods, etc.
50 views

### What is the significance of a $\chi^2$ analysis?

What is the merit of $\chi^2$ analysis in the laboratory experiments? Why is so much emphasis put on it?
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### 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 ...
1k 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 ...
183 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 ...
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 ...
63 views

### Problem with denoising BICEP2 data?

This question pertains to this article which talks about why the BICEP2 measurements of B-mode polarization in Cosmic microwave background radiation turned out to be noise from galactic stardust. They ...
61 views

### Gamma spectroscopy - Fitted Singlet

I'm using some gamma acquisition and analysis software. When I ask the software to do some sort of Nuclide Identification, almost every single peak in the generated output is marked with "F". ...
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### How experimentalists put bounds on new physics at the LHC?

I would like to understand how experimentalists search for new physics at the LHC. Lets imagine I want to use the LHC data to put a bound on the coupling of some new physics effective operator, say, ...
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### NMR Analysis of Ethylene glycol [closed]

I have the spectrum obtained by an NMR analysis of Ethylene glycol : I would like to explain the number of peaks in this spectrum, and assign them to the proton spins present in the molecule. I ...
136 views

### Interpreting the results

I have preformed the muon lifetime experiment at my uni's lab, and got the data. It's text file with 8190 numbers. My TDC unit was set so that the time gates were at 10 $\mu s$, and it has 8192 ...
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### Uncertainty in Acceleration given the uncertainty in position

I had a motion detector record the position of a dynamics cart and automatically plot Position vs Time and Velocity vs Time plots in Logger Pro on the computer. If the instrument uncertainty in ...
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### What software programs are recommended for background extraction and peak fitting?

I have an energy spectrum for various gamma sources. What software programs are recommended for background extraction and peak fitting in this case?
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### Normalize accelerometer data based on non-central location

I am trying to "normalize" accelerometer data for a sensor that is not centered on a car. In the image below, you can see how centripetal force changes based on location. In my case, I only have one ...
469 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). ...
380 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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### 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, ...
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### Error in total counts

I'm performing a radioactivity experiment where I measure a specific number of counts in some time period t. Later on I take the total count rate. (Number of counts/time: $N/t$) I'm supposed to find ...
133 views

### Log of a quantity and graphs in log-scale

Is there any difference between taking the logarithm of a quantity, and plotting a quantity in logarithmic scale?
63 views

### How do I make a Gaussian process generate a stream of events?

I would like to generate a stream of "random" gaussian events (on for event - off for no-event) that obeys a set standard deviation and mean. what algorithm could I use? thank you
1k views

### Coherent intermediate scattering function from simulations

I want to calculate the coherent intermediate scattering function, $S_{\text{coh}} (\mathbf{Q},t)$, from a molecular dynamics trajectory, based on its definition. The definition of the function is: ...
198 views

### Collection Efficiency of Photon

I am currently reading this paper: http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.112.116802#references In the second column of text in page 2, the author makes various claims about the ...
146 views

### Variance of Nested Experimental Uncertainty

I have to find the uncertainty of a quantity $Q$ doing two mean values. For example for a set of parameters I measure ten times $Q$, I obtain a mean value $Q_1$ and variance ${\rm Var}(Q_1)$. Then for ...
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### Graphing measurements with uncertainties

I need to draw a graph of measurements of time for a ball to drop on an inclined plane, with error bars, along with lines of best and worst fit. The problem is that I need to do this on the computer ...
43 views

### Linear Regressions vs Algebra & Averaging in Solving for a Constant

I'm current taking AP Physics, and in both of the labs performed so far (Snell's Law/Refraction and Galileo's Inclined Plane), I have been trying to calculate some constant from a linear relationship ...
I have some data that I can tell visually that scales like a power law. However, the $x\rightarrow \infty$ and $y\rightarrow \infty$ asymptotes of the data are nonzero. I should thus fit the data to ...