Read about error analysis | 29 Discussions | Page 1

  1. Amy_93

    I Statistic uncertainties in cross section plots - how to calculate?

    Hi there, I hope I chose the right forum for my question. So, basically, I'm doing an analysis measuring the number of signal particles in a certain momentum bin i, and doing two corrections: Nsig, i=M*(Nmeas, i-Nbkg, i) Here, M is a matrix covering PID correction and PID efficiencies, and...
  2. S

    Half-life error analysis

    What is meant by the constant background and how would one deduce the half-life IF not from the fit?
  3. K

    Uncertainties in a set of measurements

    Suppose I measure the distance between two objects for three trials. The two objects then get farther away, and I measure the distance between them again for three trials. I repeat this for 3 more different distances, getting a total of 15 measurements (3 trials for 5 distances). I then compute...
  4. C

    How to compare two measurements with uncertainties in terms of sigma?

    Perhaps that statement is just saying how big the t-value is. Like, in this case: t = (1.0 - 0.98) / 0.1 = 0.1 So we can say that our measured value is within 1 sigma from the other measured value. In this case, do we just ignore the uncertainties of the other measured/reference value? It's...
  5. J

    B Questions Regarding the Fundamental Rules of Error Analysis

    (A)My textbook states the following : (1) The example explaining the italicised statement is rather confusing. My understanding of the statement is that we need to include one extra significant figure than what the relevant rule requires us to round off to, for intermediate...
  6. J

    Trivial question on differentiating logarithms

    My Question : Shouldn't differentiating ##-log B## give ##\frac{-\delta B}{B}##? (Note : A, B and Z are variables not constants) By extension for ##Z=A^a \,B^b\, C^c## where ##c## is negative, should ##\frac{\Delta Z}Z=|a|\frac{\Delta A}A+|b|\frac{\Delta B}B-|c|\frac{\Delta C}C##?
  7. A

    Error of an instrument

    Homework Statement For my lab report I am asked to calculate the error of a couple of measurements which I did with a lux meter. I know that the lux meter has tolerance(or accuracy?) 5%. The instrument is digital and it's last digit is 0.1. The maximum reading is 47.5 lux. Homework Equations ...
  8. CricK0es

    Uncertainty of a chosen value

    Homework Statement I have taken 5 sets of readings of voltage against angle for an experiment to determine specific rotation. (I'm using the maxima to determine the phase shift) So, having averaged these values and determined the maximum, I can then trace back to the angle at which this...
  9. Roger Dodger

    B Trueness and Bias

    Can someone explain the difference between trueness and bias, as used in measurement?
  10. CricK0es

    Using STdev wrong or apparatus error?

    Homework Statement I have 3 (n) measurements of the radius of a capillary tube, and I'm wondering whether I should take the STDev of these values and then divide by sqrt(n-1) to obtain a standard error, and use this as my error on the mean... or Do I propagate the apparatus error through and...
  11. Hi Im Paul

    Excel Error Bars

    I'm currently writing a paper over an experiment I did for class and I have a very stupid question over I need clarification on before I continue. I am using excel to graph out data, and I have determined that the error in my Length is .001 m. However, I am graphing the inverse of length to...
  12. S

    MATLAB Weighting data points with fitted curve in Matlab

    Hi all, I'm currently in the middle of performing an experiment for the final project of my MSc, and I have a question about how I should go about weighting the data when fitting a curve to it using the matlab fitting tool. Firstly, a bit of background about the problem. I am seeing how low...
  13. Nikhil Rajagopalan

    Error Analysis of wall thickness

    Homework Statement The internal and external diameter of a hollow cylinder are measured with the help of a vernier calipers. Their values are (3.87 ± 0.01) cm and (4.23 ± 0.01) cm respectively. The thickness of the wall of the cylinder is ? Homework Equations Thickness of cylinder wall= 1/2...
  14. baldbrain

    How do I use the number of oscillations given?

    Homework Statement The length of a simple pendulum is about 100 cm known to have an accuracy of 1 mm. Its period of oscillation is 2 s determined by measuring the time for 100 oscillations using a clock of 0.1 s resolution. What is the accuracy in the determined value of g? (a) 0.2%...
  15. Nikhil N

    How to make a hardware setup for monitoring BER of modbus

    I have to devices in communication with modbus protocol. Master is PC and slave is compressor(100ft line,RS485 standard, modbus RTU protocol). I have to build a setup which will show how much the error in communication. I am coupling some white noise to the line and some burst signals too. I...
  16. T

    I Linear regression on data collection error

    Hi I've collected few sets of data and obtained significant different linear regression (R^2) in 2 particular sets of data . Does that indicates the 2 sets of data is not validated which might due to data collection error? For example, 20 sets of data contain linear regression of 0.900+...
  17. G

    Significant Figures & Error Analysis

    Hi, I've just had my first lab in physics and I'm having a bit of trouble understanding how to determine the significant figures of my final answers and transforming them in scientific notation. For example: Homework Statement [/B] I had to measure three sides of a parallelepiped with a...
  18. pangru

    Error Calculatoin

    Homework Statement I have to shot 100(±5) to kill 50. how many shots I need to kill 1 bird? Homework Equations The Attempt at a Solution 100±5/50 = 2±0.1 this solution is so simple, I think it is not right - is it? :rolleyes:
  19. Jefffff

    Best Method of Analyzing Experimental Percent Error

    Homework Statement I have performed a chemistry experiment where I analyzed how the diluting of two reactants with the same volume and initial concentration impacts the percent yield of a precipitate product. Thus my IV was concentration and my DV was percent yield. My question is what is the...
  20. S

    I Why is the standard deviation the error on the singular meas

    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 is one fundamental thing about ##\sigma## that I read but I could not understand. >In a series...
  21. K

    I Calculating the error in <x^2> from the error in <x> (Molecular Dynamics)

    Hi, does anyone know of an easy way to calculate the error in <x^2> from the error in <x>? I am running a molecular dynamics simulation and trying to work out the error in the fluctuation of kinetic energy <dEk> = <3/2NT^2> - <3/2NT>^2 from the error in <T>. Thanks in advance
  22. B

    I Error propagation estimation

    I have a physical quantity A defined as ##A=(74.5 B^2*(M+N))^{1/3}## where B, M, N and relative uncertainties are given. And M and N are dependent on B. Could you show me how to calculate and estimation for the uncertainty on A? Thanks a lot
  23. O

    Calculating errors after curve fitting (linearizing) graphs

    Homework Statement I did a lab this week measuring periods of swings of a simple pendulum. We need to curve fit the equation T=k*l^n and we got ln(T)=n*ln(l)+ln(k), and we need to plot the data we collected into the linear graph, meaning out y axes is ln(T) and our x axes is ln(l). So far all...
  24. J

    I need help in deciding what my error bars should be

    So, we did an experiment to find the dissolved oxygen concentration in % over time in a stirred tank reactor at 2 different flow rates and at 3 different agitator speeds. We did not do any repeat measurements, it was just one reading per condition. Now I am confused what sort of error bars I...
  25. Alejandro Golob

    Error Propogation for Half-Life

    In this homework question we are told to calculate the half-life of an isotope based on count-rates before and after a given time interval, the relevant equation is given below. Half-life = t1/2 = tln(2)/ln (A/A0) The second part asks to determine the standard deviation of the half-life due...
  26. Ryaners

    Another Error Analysis Question - how to go about it?

    Hi folks, apologies if this is in the wrong forum. I'm a new undergrad physics student and I'm having trouble figuring out how to 'do' error analysis. (I had a quick look through some similar posts here & am still none the wiser.) I'll use my recent lab experiment on Resonance in a Tube as an...
  27. S

    How to round in error analysis

    Hi, to start with my questions I will show you what I have done so far. (23.56+/-0.05) km/h x (56.3+/-0.4) h So I ended up with (1326.428+/-12.234) km But I know the real answer is (1330+/-10) km What I dont understand is how I would round to that answer. I do not know what I have to look...
  28. SalfordPhysics

    Simple error analysis

    Homework Statement A series of 5 measurements of Y are recorded with increasing X. (i.e. gradient has units Y/X) The error in measurement of Y is ±0.05 The error in measurement of X is ±0.005. How is the error in the gradient calculated? Homework Equations - measurements[/B] Y | X...
  29. L

    Calculating Experimental Error

    Homework Statement I am writing a lab report for an X-ray diffraction. I have been attempting to come up with an equation for the error using formulas some people from college gave me and also some I found on wikipedia but I am quite sure I am doing it wrong. The only variable is the angle...