Skip to main content
M
mali-21-Visitor
1-Visitor
July 6, 2015
Solved

How can i find the best distribution: weibull or exponential distribution for this data?

  • July 6, 2015
  • 3 replies
  • 5472 views

Hi everyone

can anyone help me to find the best distribution: weibull or exponential distribution for this data using Mathcad, please?

1.393    0.66    1.032    0.336    1.451    0.489    1.123    1.789    1.542    0.051    1.654    2.813    0.736    0.637    1.477    0.859    2.017    0.391    0.754    0.26    0.127    0.725    0.842   0.28    0.396    0.022    0.623    1.205    0.312    0.986    0.534    2.818    1.184    0.656    0.315    0.806    0.444    0.848    0.443    0.64    0.456    0.678    1.527    0.901    0.758    0.434   1.468    0.795    0.503    1.541

i want the parameters for both of them please

thank for all

Best answer by StuartBruff

Mohamed Ali wrote:

Hi everyone

can anyone help me to find the best distribution: weibull or exponential distribution for this data using Mathcad, please?

1.393    0.66    1.032    0.336    1.451    0.489    1.123    1.789    1.542    0.051    1.654    2.813    0.736    0.637    1.477    0.859    2.017    0.391    0.754    0.26    0.127    0.725    0.842   0.28    0.396    0.022    0.623    1.205    0.312    0.986    0.534    2.818    1.184    0.656    0.315    0.806    0.444    0.848    0.443    0.64    0.456    0.678    1.527    0.901    0.758    0.434   1.468    0.795    0.503    1.541

i want the parameters for both of them please

thank for all

With so few data points, you could probably(!) fit anything you wanted to it.   If you open my worksheet on your other recent thread, you type in your data in place of the test data and see what it looks like.  It looks as though the weibull is a better shape than the exponential. 

You could use genfit to try and estimate the best fit value for the shape parameter s, but I suspect that you'd be better off adjusting your data to get rid of the large outlier (if that's what it is) in the tail of the distribution; othewise, the shape looks to be a poorer fit to the main part of the histogram.

Stuart

3 replies

L
LucMeekes23-Emerald IV
23-Emerald IV
July 6, 2015

How about this:

I find the best correlation for a lognormal distribution, but one might argue that Weibull fits better.

Success!

Luc

    S
    StuartBruff23-Emerald VAnswer
    23-Emerald V
    July 6, 2015

    Mohamed Ali wrote:

    Hi everyone

    can anyone help me to find the best distribution: weibull or exponential distribution for this data using Mathcad, please?

    1.393    0.66    1.032    0.336    1.451    0.489    1.123    1.789    1.542    0.051    1.654    2.813    0.736    0.637    1.477    0.859    2.017    0.391    0.754    0.26    0.127    0.725    0.842   0.28    0.396    0.022    0.623    1.205    0.312    0.986    0.534    2.818    1.184    0.656    0.315    0.806    0.444    0.848    0.443    0.64    0.456    0.678    1.527    0.901    0.758    0.434   1.468    0.795    0.503    1.541

    i want the parameters for both of them please

    thank for all

    With so few data points, you could probably(!) fit anything you wanted to it.   If you open my worksheet on your other recent thread, you type in your data in place of the test data and see what it looks like.  It looks as though the weibull is a better shape than the exponential. 

    You could use genfit to try and estimate the best fit value for the shape parameter s, but I suspect that you'd be better off adjusting your data to get rid of the large outlier (if that's what it is) in the tail of the distribution; othewise, the shape looks to be a poorer fit to the main part of the histogram.

    Stuart

      M
      mali-21-VisitorAuthor
      1-Visitor
      July 6, 2015

      Thanks for reply

      but how did you graph the dweibull(x,s) although we did not know the value of s ?

      S
      StuartBruff23-Emerald V
      23-Emerald V
      July 8, 2015

      Mohamed Ali wrote:

      Thanks for reply

      but how did you graph the dweibull(x,s) although we did not know the value of s ?

      I just guessed from the look of the curve and chose 2 (or, rather, left it at the value I'd used to generate the dummy test data earlier on in the worksheet).   The genfit function should then have improved upon that value.

      Stuart

        J
        jkowalski1-Visitor
        1-Visitor
        July 8, 2015

        These are just my thoughts.I have a Mathcad 15 but does not work on Windows 8.1.I tried this in the Mathematica software. There is such a function called "DistributionFitTest"  calculates the "p" probability and tested whether data is distributed. A small p-value suggests that it is unlikely that the data came from dist.

        • WeibullDistribution p = 0.422665.
        • ExponentialDistribution p = 0.00122985.
        • LogNormalDistribution p = 0.0165806.
        • NoncentralFRatioDistribution p = 0.676676.

        So "NoncentralFRatioDistribution" fits is  best.Of course, I'not checked all distributions , it may be better fit there are so many.

        ryf.png

          Terms & ConditionsAccessibility statement