Questions tagged [data-analysis]

Use for question relating the the techniques of data analysis.

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1answer
24 views

How to find the period of a pendulum knowing only its speed and maximum arc-length?

I am writing a program to give me the period of a pendulum, the program can measure the speed of the pendulum at every 1/60th of a second (Limited by camera frame-rate.) Is it possible to know the ...
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0answers
55 views

Discovery of a new particle [closed]

Why do we only confirm the discovery of new particle when standard deviation is approx $5\sigma$. What is the probability associated with $5\sigma$ standard deviation. Be little rigorous.
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2answers
36 views

Simplifying acoustic test procedure — don't want to bother neighbors with party!

I am having a party and would like to keep disturbing neighbors to a minimum, but maximize the volume we can get away with. I devised a quick n' dirty test plan to generate some frequency response ...
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1answer
32 views

Determine speed of moving vehicle from video taken in a moving vehicle [closed]

I have dash camera footage from my motorcycle where the police were speeding illegally in dangerous conditions. I know my speedo is 7% over so if it reads 107KPH a radar gun will ping me at 100KPH. I ...
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37 views

How to find the integrated luminosity for a 5$\sigma$ discovery?

I was thinking about the procedure needed for the discovery of a new particle. Suppose a data-analysis aims at searching for a new resonance X decaying to two electrons after collecting 20 fb$^{-1}$ ...
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3answers
63 views

Should we include instrumental uncertainty when calculating the uncertainty of a measurement?

Imagine we are measuring the period $T$ of a pendulum using a stopwatch The stopwatch has an inerent instrumental uncertainty (e.g. 0.1s) let's keep this fact in mind Due to random error (let's ...
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1answer
36 views

Uncertainty in data from star databases

I have students who are pulling data from various astronomical databases like SIMBAD or the Binary Star Database and then using that data to determine correlations between certain properties. My ...
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4answers
982 views

Help interpreting “five sigma” standard?

So, I am coming from a math/stats background. I was just wondering about this in the abstract, and tried Googling around, and came across this article which says the following regarding some ...
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1answer
19 views

Polynomial regression and errors weighted with square root of reduced chi square

I conducted a polynomial regression of the form $y(x) = A+Bx + Bx^2$, and would like to obtain parameters $A$, $B$ and $C$ and their respective errors/confidence level. The reduced chi square is less ...
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1answer
21 views

How to extract velocity and acceleration from $N$-body simulation data?

I have data from an $N$-body simulation and want to do some data analysis. I would like to extract the velocity and acceleration of each particle. The data consists only of the positions of each ...
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4answers
100 views

Is the Least Squares Fit always the accepted Fit in Physics?

Is the Least Squares Fit always the accepted Fit in an experiment? Suppose you have $N$ data points and a function $f$ with some parameters. There is a one Least Square sum, it may be obtained for ...
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Intuition re. log scale versus linear scale

I have a dataset with the speed of movement of two sets of particles (the red, slower, and the blue, faster) as calculated by the diffusion constant. Below is a histogram, on the left on linear scale ...
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3answers
21 views

How to display an measurement results with error bar given huge number of digital measurements? [closed]

I need to measure the flow rate using a flow meter. This flow meter collects 6000 data points over the course of 5 minutes for every temperature of our experiments. I repeat this experiment at ...
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25 views

$S$-Parameter Phase in Matlab

I'm trying to plot the phase of S-parameters on Matlab. The data I have is the coupling matrix (M) of the system and from that I have extracted S11 and S21 (column 1 in image is frequency and column 2 ...
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1answer
47 views

How to calculate the amount of standards deviations a measure is from another value

I have a theoretical value $\gamma_t$ and a measured values $\gamma_m$, with uncertainties $\sigma_{\gamma_t}$ and $\sigma_{\gamma_m}$ respectively. If the errorbars of $\gamma_m$ is inside of $\...
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1answer
60 views

Sigma Significance in Particle Physics and Beyond [closed]

Why is a 5 sigma confidence level enough to solidify an experimental result as not being a statistical fluke in particle physics? Other branches of science have different sigma values for which they ...
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1answer
81 views

What is the strongest result that has subsequently been shown to just be a statistical glitch?

While reading up on the $g-2$ result, I noticed that the authors stopped short of announcing a definitive result because they only had 4.2 sigma of confidence rather than the 5 that is the standard ...
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0answers
31 views

Looking for the experimental spherical harmonics coefficients of the CMB

Using Mathematica, I would like to plot the Cosmic Microwave Background has a spherical harmonics decomposition. As experimental data, I need to know the values of the $a_{l,m}$ coefficients in the ...
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1answer
58 views

Data rate of Atlas and CMS, LHC's detectors too slow?

There is a technical question I always curious about to ask a CERN expert? I have read, http://nordberg.web.cern.ch/PAPERS/JINST08.pdf, page 5, that the data sampling rate, number of stills taken from ...
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3answers
58 views

Calculate the slope of a straight line from experimental points [closed]

Draw a straight line from the experimental points so that the scatter of the experimental points is minimal. Having determined the slope of the resulting straight line. How should I do it? I ...
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2answers
159 views

Does the recent “3-sigma” result at LHCb account for the number of different tests of beyond standard model physics that have been done?

Recently there has been quite a lot of media interest generated by a reported observation of beyond-standard-model physics at the LHC with a "three sigma" degree of statistical significance. ...
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Resource request for experimental physics and data handling

When solving questions in olympiad physics, I come across problems on experiments, data, errors, drawing graphs and extracting information from given graphs, etc. Is there any good book/resource for ...
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13 views

XRF experimental data?

I am trying to test my model to subtract background from Xray Spectrum. I do not have access to any equipment. Where may I find XRF experimental data? Detector response data? etc. Does one know a ...
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0answers
38 views

What did Freeman Dyson mean when he said this? [duplicate]

In this video, Freeman Dyson, when speaking of Fermi said the following thing, "...what does he think about the numerical agreement, and he said, 'How many parameters did you use for the fitting?...
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1answer
63 views

Uncertainty on intersection of two lines of best fit

I am doing some lab work, and one of the values I have to find is the x-value of the intersection of the two lines of best fit to some of the experimental data. I have the values for their slopes and ...
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1answer
175 views

Error propagation with Log base 10 [closed]

I have some data and some errors for the data. The task I have been given is to $\log_{10}$ both sets of data, and then deal with the errors to plot a graph. For natural logarithms, this is easier as (...
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30 views

Analytical expression for uncertainty in resonance frequency

I'm asked to write an analytical expression for the uncertainty in the ratio of the resonance frequency of some "string" to the mode of vibration, which works out to always be equivalent to ...
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3answers
75 views

Clean lab data set

In a experiment I have a set of values for position an time (t,x) but due to the lab conditions the set is a little noise (you know, limitations, I cannot have infinite precision, thermal noise, the ...
161
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20answers
11k views

How do you make more precise instruments while only using less precise instruments?

I'm not sure where this question should go, but I think this site is as good as any. When humankind started out, all we had was sticks and stones. Today we have electron microscopes, gigapixel cameras ...
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1answer
34 views

What qualifies an x-ray line as “useful for quantification” in a material's x-ray analysis?

Original question: Knowing the energy values for the different X-ray lines for Mo and for S in the analysis of bulk MoS$_2$ ($K_{\alpha 1}$, $K_{\alpha 2}$$K_{\beta1}$, $L_{\alpha 1}$, $L_{\beta1}$, ...
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2answers
160 views

How to draw the best fitting line on Hooke's Model for a spring?

I just started learning about Hooke's Law and calculating the slope of a force vs. extension graph of a spring for the spring constant. If I conduct an experiment and the extension length of my spring ...
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2answers
17 views

Reality check on method of getting results from an instrument with high hysteresis?

Given an instrument that has either a genuine hysteresis, or possibly just internal friction, would the following method work to get better precision. (I don't really care about accuracy. I want to ...
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How to check the particle rate of $1\ m^{-2}.s^{-1}$ at an energy of $10^{12}\ TeV$ from the “Swordy plot”? [duplicate]

On this web page, we see the so-called "swordy plot" https://www.quantamagazine.org/ultrahigh-energy-cosmic-rays-traced-to-hotspot-20150514/ At an energy of $10^{12}\ eV=1\ TeV$, we read ...
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1answer
32 views

How to calculate uncertainty of rounded data [closed]

I have been seriously confused with the following text for a short while. Suppose that three teachers have timed the school 100 m sprint race and have recorded times of 12.3, 12.5, and 12.6 s for the ...
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1answer
28 views

When linearizing a data point of an inverse relationship, how does its uncertainty change?

I have a question regarding data analysis and uncertainties regarding my physics experiment. Essentially, I conducted an experiment to determine the relationship between salt concentration and ...
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0answers
18 views

How to evaluate the parallax error in the measure of diffraction rings' diameter?

I have to estimate with an image analysis the diameter of the rings generated by the diffraction of an electron beam with a polycrystalline graphite target. The pattern is made visible by a ...
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1answer
76 views

Millikan oil drop experiment

I had a question about the Millikan Oil drop experiment. I did the experiment for my physics class where we had to determine the voltage that would make the droplet stationary. We did this ten times, ...
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1answer
36 views

Determining the error in gradient through least fit of data

I am try to measure the error in the slope of the black dots. To do this I performed a linear regression to the data using from scipy.optimize import curve_fit on ...
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2answers
57 views

How to work out with how many sigma confidence my measurement confirms the theory?

Suppose by a theory a certain value should be 1. I make an experiment in which I measure it to be 1.1 ± 0.2, where the ± 0.2 are 1 sigma Gaussian errors? Obviously I can see that the theoretical value ...
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2answers
43 views

How to compare several experimental measurements and their uncertainties?

I have a basic question about how to make the comparison of different measurements. For example, suppose I have measured the focal length of a convergent lens using three different methods, $A$ and $B$...
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1answer
93 views

Uncertainty of polar Coordinates

I am trying to do some error propagation to find the error on polar coordinates starting with cartesian coordinates. Using the equations found in Hughes and Hase, "Measurements and their ...
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0answers
29 views

Model parameter derivation, least squares fitting vs solving systems of equations

PS: Let me preface this with I barely have an idea how to ask this question so bare with my ramblings. I'm trying to fit a 5 parameter model to gravitational lenses. For this I have 2 classes of ...
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0answers
42 views

How to calculate the Likelihood function of a gaussian pdf

Suppose a model for a flux of (astro)particles $\dot \Phi(E,t)$ (from a supernovae) that depends on particle energy $E$ and time $t$ (from beginning of explosion), and 3 free parameters $T_a, M_a, \...
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7 views

Mean of gradients or gradient of mean points

I have 5 repeat measurements of a dependent variable for each of 5 values of an independent variable. To find the gradient and estimate its error, is it better to plot the 5 mean points and find the ...
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2answers
55 views

What do I set for the standard deviation of a measurement, if the value is not normally distributed?

I took multiple $B$ measurements for a constant $A$ value, which I simultaneously measured. $A$ (in my case the resistance of a temperature sensor) was controlled by a PID controlled and slowly ...
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0answers
29 views

FFT on a signal with a length that is not a multiple of the period of its harmonics

I was very surprised to find an apparent limitation to a FFT on a simple signal. Let's consider a timeseries made of L=100 points, and simply composed of the sum of two sinus waves: one with a ...
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1answer
19 views

How can I cluster infrared spectra?

This is sorta a cross-post from my post in StackOverflow. Although, rather than seeking help with the code I'm here asking for help with a physical/mathematical/statistical problem associated with the ...
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2answers
32 views

What is the difference between horizontal units and horizontal scale at an oscilloscope?

This is a picture of the data of a given measurement by an oscilloscope. I would like to know what the difference between horizontal units and horizontal scale at an oscilloscope is. I would be so so ...
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1answer
214 views

Why do I have to draw a big triangle to determine the gradient of a straight line using the slope triangle method?

I'm an igsce student, I'm taking igsce OL phyiscs. It's stated in my book that after I draw a graph and the line of best fit, I should get the gradient by choosing two points then form a right angel ...
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0answers
26 views

Magnetic flux as a function of distance experiment

For my electrical engineering senior design I created an experiment to test magnetic flux (more voltage) increase from a material in a coil of wire. There is a large sending coil with A.C. voltage and ...

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