Template:Ald mean: Difference between revisions
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====The Mean or MTTF==== | ====The Mean or MTTF==== | ||
: | :* The mean of the lognormal distribution, <math>\bar{T}</math>, is given by: | ||
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: | :* The mean of the natural logarithms of the failure times, <math>{{\bar{T}}^{^{\prime }}}</math>, in terms of <math>\bar{T}</math> and <math>{{\sigma }_{T}}</math> is given by: | ||
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::<math>{{\bar{T}}^{\prime }}=\ln \left( {\bar{T}} \right)-\frac{1}{2}\ln \left( \frac{\sigma _{T}^{2}}{{{{\bar{T}}}^{2}}}+1 \right)</math> | ::<math>{{\bar{T}}^{\prime }}=\ln \left( {\bar{T}} \right)-\frac{1}{2}\ln \left( \frac{\sigma _{T}^{2}}{{{{\bar{T}}}^{2}}}+1 \right)</math> | ||
<br> | <br> | ||
Revision as of 16:51, 7 March 2012
The Mean or MTTF
- The mean of the lognormal distribution, [math]\displaystyle{ \bar{T} }[/math], is given by:
- [math]\displaystyle{ \bar{T}={{e}^{\bar{{T}'}+\tfrac{1}{2}\sigma _{{{T}'}}^{2}}} }[/math]
- The mean of the natural logarithms of the failure times, [math]\displaystyle{ {{\bar{T}}^{^{\prime }}} }[/math], in terms of [math]\displaystyle{ \bar{T} }[/math] and [math]\displaystyle{ {{\sigma }_{T}} }[/math] is given by:
- [math]\displaystyle{ {{\bar{T}}^{\prime }}=\ln \left( {\bar{T}} \right)-\frac{1}{2}\ln \left( \frac{\sigma _{T}^{2}}{{{{\bar{T}}}^{2}}}+1 \right) }[/math]