Error Definition and 998 Threads

An error (from the Latin error, meaning "wandering") is an action which is inaccurate or incorrect. In some usages, an error is synonymous with a mistake.
In statistics, "error" refers to the difference between the value which has been computed and the correct value. An error could result in failure or in a deviation from the intended performance or behavior.

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  1. joneall

    Relativity Is There an Error in Hartle's Fig. 7.11 Caption Regarding Normals and Tangents?

    A question concerning FIg. 7.11 on page 173. It seems to me, in light of what is said on the preceding page about null surfaces, that he has interchanged "normal" and "tangent" in the third and fourth sentences of the figure caption. I would say: "The tangent to the surface l lies in the...
  2. J

    I 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...
  3. kelvin490

    Fortran Input/Output error with error code -5

    I got a problem running my FORTRAN program in high performance computer cluster. It runs well in my PC but I want to have mass production of data with different initial conditions so I put it in a cluster node with eight cores, simulate eight sets of data. The program can run without problem...
  4. H

    Error in Srednicki renormalization?

    On page 164-165 of srednicki's printed version (chapter 27) on other renormalization schemes, he arrives at the equation $$m_{ph}^{2} = m^2 \left [1 \left ( +\frac{5}{12}\alpha(ln \frac{\mu^2}{m^2}) +c' \right ) + O(\alpha^2)\right]$$ But after taking a log and dividing by 2 he arrives at...
  5. 24forChromium

    How to address experimental error in conclusion

    I am writing an essay which includes the experimental "verification" of a theory. As it turns out, the theory was able to predict a certain variable F's direction of change (i.e. increase or decrease across two data points) "correctly" for 90% of the time, and predicts the value of F at each...
  6. A

    Error in My Code: Undefined Symbols for x86_64

    I have received this error : Undefined symbols for architecture x86_64: "start", referenced from: -u command line option (maybe you meant: __gfortrani_library_start) ld: symbol(s) not found for architecture x86_64 collect2: error: ld returned 1 exit status what is this mean?? the code is...
  7. P

    What Is the Error in Counting Rate Per Second for Gamma Photons?

    Homework Statement A detector is used to count the number of gamma photons emitted by a radioactive source. If the number of counts recorded in exactly 20 seconds is 10000, the error in counting rate per second is (a) 5.0 (b) 22.4 (c) 44.7 (d) 220.0 Homework EquationsThe Attempt at a Solution...
  8. Bera Icli

    Stiffness/Residual Vector Error - NaN/Inf findings

    Hi, I am especially writing this, because there is no specific explanation I found online. I checked the BCs and other variables, but could not find any mistakes. I am working on a semiconductor device that is basically n-doped homogeneously, has sizes 50um-15nm, and with a drain voltage 1V...
  9. J

    Error while accessing board through TTL

    I am trying to access a console with my TTL (cp2102 ) but I am getting following error. What could be wrong? I am trying J4 point for TTL. I am connecting ground to ground, Rx to TX and TX to RX. Only with this combination I am getting the log as posted below. 3.3V is not needed in my case as...
  10. GiantSheeps

    What Are Common Sources of Error in Flame Test Labs?

    Homework Statement In a flame test lab, where different unknown substances are heated and the identity of the substance is determined by the color emitted, what can be some sources of error? Homework Equations n/a The Attempt at a Solution I need three sources of error, and so far I have...
  11. phy9

    Excel formula for rounding a value & error

    I'm having a physics lab in which a report needs to be submitted after an experiment. The experiment includes many measurements: values with their errors. I need to round the error up to 2 significant digits, and then to round the value up to to the amount of digits that the error is presented...
  12. R

    Importance of Angle in Light Spectrometry for Reflectance Measurements

    Homework Statement Hello, I've been using a light spectrometer to try to measure the reflectance of a sample of a protein I have on a glass slide. I followed the manual's instructions and first took a dark spectrum and a reference spectrum. However, the intensity was too high (far above the...
  13. 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...
  14. R

    Evaluating Total Error for Continuous Functions f and g

    Consider two functions f, g that take on values at t=0, t=1, t=2. Then the total error between them is: total error = mod(f(0)-g(0)) + mod(f(1)-g(1)) + mod(f(2)-g(2)) where mod is short for module. This seems reasonable enough. Now, consider the two functions to be continuous on [0,2]. What...
  15. C

    Error Propagation in Mass Flow Rates

    I tried posting this question in this forum a couple of weeks ago, but didn't get an answer to my question. I'm going to try posting it again using the formatting template so that it is hopefully clearer. I am also not sure if this is the right forum to be posting this in. It is a problem I ran...
  16. lep11

    Derive error formula for Lambda (25 C)

    In physics lab course I measured equivalence conductivity of NaCl in infinite dilution Λ0 as a function of temperature T. So I have observations (T, Λ0) and fitted a line using the least squares method in Ms excel (lol :oldbiggrin:). The formula of the line is Λ0(T)=c0+c1T, where c0 and c1 are...
  17. T

    Hypothesis test and finding type 2 error probability

    Homework Statement From extensive records it is known that the duration of treating a disease by a standard therapy has a mean of 15 days. It is claimed that a new therapy can reduce the treatment time. To test this claim, the new therapy is to be tried on 70 patients and their times to recovery...
  18. R

    Calculating Uncertainty for Gravitational Potential and Kinetic Energy Equations

    Homework Statement I am writing a lab report and I need to calculate the uncertainty error for Gravitational Potential Energy and Kinetic Energy. The Professor told us that the margin of uncertainty for time is +- 0.025 seconds, margin for height is +- 0.001 meters, margin for mass is +-0.001...
  19. S

    Errors: Random, Systematic, and Human

    Homework Statement Hello! In our class, we just completed a lab on momentum and energy conservation in collisions. It was a computer simulation. Although, for the lab report, the teacher wants us to write the random, systematic, and human errors. Can someone describe what each error means? What...
  20. NicolasPan

    Comp Sci Error while calculating arc length of curve in Fortran

    The program must calculate the length of the curve of ƒ=3.1*x^2-5.3/x between x=1/2 and x=3/2.The legth should be calculated as the sum of n line segments starting with n=1 and ending with n=20. I really can't find why the result I'm getting is wrong.Thanks in advance I am giving you the code...
  21. J

    4.2 Acceleration due to gravity lab error

    Homework Statement My best fit-line for my average velocity time graph doesn't seem to start at 0 m/s. I have no idea how to explain this in my conclusion - http://imgur.com/zniGGkw. This lab was conducted by using a recording timer, and a mass. We started the recording timer first, then let...
  22. 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...
  23. C

    Error Propagation - Reconciling Two Approaches

    Hi, I am trying to find the error propagated by calculating the sum of a set of mass flow rates collected over the same length of time. The sum of mass flow rates can be calculated with two approaches, since the collection time is the same for all of them. Approach (1) is adding up all of the...
  24. evinda

    MHB Crank-Nicolson: Proving Max Bound of $|T_i^{n+\frac{1}{2}}|$

    Hello! (Wave) I want to show that for the Crank-Nicolson method, the following holds: $|T_i^{n+\frac{1}{2}}| \leq \frac{\tau^2}{12} M_{ttt}+\frac{h^2}{12}M_{xxxx}$, where $M_{ttt}=||u_{ttt}||_{\infty}, M_{xxxx}=||u_{xxxx}||_{\infty}$ and...
  25. evinda

    MATLAB Troubleshooting a MATLAB Error: Inner Matrix Dimensions Must Agree

    Hello! (Wave) I have written the following code in matlab: function v=uexact(x,t) v=sin(2*pi*x)*exp(-4*pi^2*t); end function [ex]=test3 h = 1/50; T=1/2500; x=0:h:1; t=0:T:1; ex=uexact(x,t); end I...
  26. A

    Error in Natural Frequency (Lab)

    So I just did a lab on resonant frequency, and have to find the error of the period: $$T = 2π\sqrt{m/k}$$ m and k were measured with an error of Δm and Δk. My teacher didn't explain well how to do errors, so I just want to know if I did this right. Prorogation of Error equations: $$y=x^n ⇒...
  27. DaveC426913

    Representing error: expected versus actual speed

    I am checking the accuracy of my speedometer. When my speedo says I'm doing 100km/h, I record an actual speed of 123km/h. When my speedo says I'm doing 60km/h, I record an actual speed of 68km/h. I have more data but it corroborates this simple example: error increases with increasing speed. I...
  28. L

    Error propagation with dependent variables

    Homework Statement Based on Microdosimetry theory, trying to figure out error propagation for a lot of quantities that are produced from radiation spectra. I am having trouble finding information on how to calculate and propagate errors when the quantities in my equations are not independent...
  29. K

    Multivariable Derivative Error

    Homework Statement f(x,y) = (xy) / (x2 + y4), when (x, y) ≠ (0,0) 0, when (x,y) = (0,0) Homework Equations Explicitly show that f(x,y) does not satisfy lim h -> 0 [ E(v,h) / ||h|| ] = 0 when v = 0 (h, v, and 0 are all vectors; I'm not sure how to put a hat on them) The Attempt at a Solution I...
  30. H

    Xcode "Thread 1: EXC_BAD_ACCESS" error

    So, I was making this simple image processing programming for the bitmap image. Like the image I upload here, that Thread 1: EXC_BAD_ACCESS occurred although the program can perfectly running when I run it on Mac Terminal and on Windows. What seems to be the problem? Since my English is not my...
  31. lep11

    Matlab data-analysis problems (systematic error, distributions)

    Homework Statement I have a few data-analysis problems due to Thursday, 1. Assume that a sandbag is dropped at different heights and the observations are (z i;ti) pairs. Physical model for a free fall is z=½gt2. Assume that the height measurement z has an additive random error v. The...
  32. H

    Fortran Solving Fortran Runtime Error 112 - Mach Number Calculation

    Hi, I try to write program to calculating mach number, with using bisection method. When I run program, fortran write to me an error in line 40. Can you help? I tried to calculating function by using wolfram sucesfully but I need to run it on fortran, An equation is 1.7795 - (0.334898 (1 + 0.2...
  33. CuppaMuons

    What should I choose as the error on x? (Curve Fitting Matlab)

    Homework Statement So I've done an experiment by scanning over a range of angle and measuring the intensity of X-Rays. There are peaks where I have X-Ray diffraction occurring and in order to do analysis I need to identify the values of angle and an error (as in the plus/minus) on this value...
  34. M

    How can I simplify error estimates for a given equation?

    Homework Statement Simplify: 1/k [(k-1) x_n+ x^k/(x_n^(k-1) )]- 1/k [(k-1)x+ x^k/x^(k-1) ] where e_n = x_n - x x_n means x subscript n e_n means e subscript n It might be easier to look at the picture I typed out in MS Word...
  35. M

    Best Method for Calculating % Error Between Two Curves?

    Hi PF! Can anyone tell me what you think the best method is to calculate the % error between two curves? My thoughts were to take $$100\frac{ \sqrt{\int_a^b (f-g)^2 \, dx}}{\int_s f \, ds}$$ where the integral in the denominator is a line integral. What are your thoughts? Thanks for looking!
  36. W

    Java Troubleshooting Error: Cannot Find Symbol in Java Code

    My program says it doesn't recognise the symbol signum(double) or sqrt(double)! I have definitely done the whole import java.lang.Math; thing. And signum and sqrt aren't symbols anyway. Is that too vague? I can post the actual code. It's only my second week learning java, so it's supposed to be...
  37. S

    Fortran Fortran (90) runtime error: End of file

    I am using fortran 90 to find the prime numbers (1-100). When I print to the console, everything works. If I try to write to an text file (.out). This is from my command line: Sues-MacBook-Air:FORTRAN sueparks$ gfortran PRIME.f90 Sues-MacBook-Air:FORTRAN sueparks$ ./MY_PRIME.out PROGRAM PRIME...
  38. T

    Derivative of an integral and error functions

    Homework Statement differentiate ∫ e^(-x*t^4)dt from -x to x with respect to x.[/B]Homework Equations erf(x) = (2/sqrt(π)) ∫e^(-t^2)dt from 0 to x. Leibniz rule. I know that ∫t^2e^(-t^2)dt from 0 to x = (√π/4)*erf(x) - (1/2)*x*e^(-x^2)[/B]The Attempt at a Solution By using Leibniz rule...
  39. M

    Is there an error in my textbook?

    Homework Statement Homework Equations Doesn't the integral of sec x tan x equal sec x? The Attempt at a Solution
  40. W

    Method for determining error in an equation

    Homework Statement Ok, so suppose I have an equation like V_out = 0.5(1 + R4/R3)(V1+V2) and I know the R3 and R4 has a tolerance of +-5%. For such an equation and similar ones, how would I estimate the possible range of values V_out? For example, I'd like to find out something like...
  41. N

    Instrument Error or Standard Deviation

    I had a question about how to properly perform error analysis on a series of distance measurements. I need to find the relative error in the distance. I was wondering, should I use the instrument uncertainty divided by the measurement (in this case, it would be 0.005m / (mean measurement)). Or...
  42. N

    Error Propagation: x/(y-z) Uncertainty

    Homework Statement Suppose you measure three numbers as follows: Homework Equations x= 200. +-2. y= 50. +-2. z= 40. +-2. where the three uncertainties are independent and random. Use step-by-step propagation to find the quantity q= x/(y-z) with its uncertainty. The Attempt at a...
  43. M

    What is the correct range for c in Taylor's Theorem error bound?

    For the error bound for taylor's theorem, for the n+1 derivative evaluated at some c which maximizes the derivative my textbook says c must be between a and x..but today my teacher said that c must be between absolute value x and negative absolute value x, which is different than I thought. An...
  44. N

    Comp Sci Java Error: "Type Mismatch" Explained

    I am programming in Eclipse and I keep seeing the error " Type mismatch: cannot convert from int to String", not only in the example I am going to provide but other programs. I've just started programming in Java. Could someone explain to me what this error exactly means? publicclassPracOne{...
  45. D

    Calculators TI-84 Rounding Error in Fraction Mode

    I had a student calculate ##\tan\left(\frac{5\pi}{6}\right)## on a TI-84 calculator and he had a rounding error in the 6th or 7th decimal place. This isn't really a big deal, but he asked and we quickly found out it was because he was in fraction display mode. I don't know too much about...
  46. maverick_76

    Understanding the Role of Error Functions in Integrals

    Okay so I was integrating an expression and ended up getting an imaginary error function in the answer. I'm not sure where to go from there, I plugged it into wolfram and the root it gave me looks nice but is that worth anything to me? The integral was being evaluated from -∞ to ∞, would I need...
  47. I

    Need clarification on sig-figs and propagation of error.

    Hello, I have a question asking me to find the volume of a rectangular prism. The dimensions are as follows: x = 20 ± 0.2 cm, y = 30 ± 0.2 cm, z = 70 ± 0.4 cm I am asked to report the answer with the correct number of significant figures and include the error. What I have so far: V = xyz =...
  48. GiantSheeps

    Experimental Error in Archimedes Principle Lab

    Homework Statement I need to find three potential reasons for my .5% error in a lab where I used the Archimedes Principle to measure the density of Iron. We only used a graduated cylinder full of water and an iron mass. I measured the water level from the meniscus. We used two different...
  49. W

    Error in Wikipedia Cavendish article

    According to Wikipedia, Cavendish was able to measure a force of 1.74E-7 N or “roughly the weight of a large grain of sand[13] of 0.13 mg” However, with my calculations using m=F/g, where g=9.81m/s/s Gives m=1.74E-7/9.81 = 1.77E-8 kg = 0.0177 mg Which is much less than 0.13 mg Am I missing...
  50. M

    Why Does Increasing Final Run Time Cause Divergence in Finite Differencing?

    hi PF! I've attached pictures to help you all see what is happening. Basically, I am running a forward time-centered space finite difference scheme, which is $${h_i^{j+1} \approx \left[ h_i^j \left( \frac{h_{i+1}^j-2h_i^j+h_{i-1}^j}{\Delta z^2} \right) + \frac{1}{2}\left(...
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