To comment on the following update, log in, then open the issue: http://www.openoffice.org/issues/show_bug.cgi?id=99800 Issue #|99800 Summary|how to use WEIBULL() integrated help and online help d |iffer Component|Spreadsheet Version|OOo 3.0.1 Platform|Unknown URL|https://bugs.launchpad.net/bugs/334197 OS/Version|All Status|NEW Status whiteboard| Keywords| Resolution| Issue type|DEFECT Priority|P3 Subcomponent|ui Assigned to|spreadsheet Reported by|ccheney
------- Additional comments from cche...@openoffice.org Tue Mar 3 04:09:21 +0000 2009 ------- >From the Ubuntu bug report: " The inline help for the WEIBULL function in Calc states that it should be used as WEIBULL(number, alpha, Beta, mode), where alpha is the scale parameter, or characteristic life of a component, and Beta is the distribution shape factor. However, the online documentation for the WEIBULL function in Calc states that it should be used as WEIBULL(number, Beta, alpha, mode), using the alpha and Beta definitions above. This method is in fact how Calc expects users to input the formula in order for it to calculate properly, but the help file makes this confusing. Entering the formula using the first notation above produces errors. Using the second notation, the correct result is obtained, but this differs from how the help file states it should be entered and also from standard definitions of the alpha and beta parameters for the Weibull distribution. For example, I would like to calculate the reliability of a component at 800 hours of service using the Weibull function. For this component, I have determined that it has an alpha (characteristic life) of 1690 hours. This means that there is a 37% chance of surviving to 1690 hours. The Beta parameter for this component is 1.37, which indicates an increasing rate of failure. According to the help file in Calc, I should enter this as "=WEIBULL(800;1690;1.37;TRUE)", however this results in a value of 1.00, which I know is wrong. Changing the last parameter to FALSE produces a #VALUE error. I know from doing this calculation by hand that the result should be 30.16%. According to the online documentation for this function, I should enter "=WEIBULL(800;1.37;1690;TRUE)". This produces the correct answer. Help files installed with Calc need to be updated to properly reflect use of this function according to the online documentation. I just realized that the parameter naming on this website is completely different than in the in-line help file. They use k to describe the shape factor (Beta, as above), and lambda to describe the scale parameter (alpha, as above). Regardless, entering the parameters as outlined on the link above produces the correct result, which is different than the help file indicates. " -- Integrated Help: WEIBULL Returns the values of the Weibull distribution. Syntax WEIBULL(Number; Alpha; Beta; C) Number is the value at which to calculate the Weibull distribution. Alpha is the Alpha parameter of the Weibull distribution. Beta is the Beta parameter of the Weibull distribution. C indicates the type of function. If C equals 0 the form of the function is calculated, if C equals 1 the distribution is calculated. Example =WEIBULL(2;1;1;1) returns 0.86. -- Online Help: http://wiki.services.openoffice.org/wiki/Documentation/How_Tos/Calc:_WEIBULL_function WEIBULL(x; k; λ; mode) The Weibull distribution is a continuous probability distribution, with parameters k > 0 (shape) and λ > 0 (scale). If mode is 1, WEIBULL calculates the probability density function of the Weibull distribution: Image:Calc_weibull1_equation.png If mode is 0, WEIBULL calculates the cumulative distribution function of the Weibull distribution: Image:Calc_weibull0_equation.png --------------------------------------------------------------------- Please do not reply to this automatically generated notification from Issue Tracker. Please log onto the website and enter your comments. http://qa.openoffice.org/issue_handling/project_issues.html#notification --------------------------------------------------------------------- To unsubscribe, e-mail: issues-unsubscr...@sc.openoffice.org For additional commands, e-mail: issues-h...@sc.openoffice.org --------------------------------------------------------------------- To unsubscribe, e-mail: allbugs-unsubscr...@openoffice.org For additional commands, e-mail: allbugs-h...@openoffice.org
