Template:Lognormal distributionrank regression on x: Difference between revisions

From ReliaWiki
Jump to navigation Jump to search
No edit summary
(Redirected page to The Lognormal Distribution)
 
(2 intermediate revisions by one other user not shown)
Line 1: Line 1:
===Rank Regression on X===
#REDIRECT [[The_Lognormal_Distribution]]
Performing a rank regression on X requires that a straight line be fitted to a set of data points such that the sum of the squares of the horizontal deviations from the points to the line is minimized.
 
Again, the first task is to bring our  <math>cdf</math>  function into a linear form. This step is exactly the same as in regression on Y analysis and Eqns. (lnorm), (yln), (aln) and (bln) apply in this case too. The deviation from the previous analysis begins on the least squares fit part, where in this case we treat  <math>x</math>  as the dependent variable and  <math>y</math>  as the independent variable. The best-fitting straight line to the data, for regression on X (see Chapter 3), is the straight line:
 
::<math>x=\widehat{a}+\widehat{b}y</math>
 
The corresponding equations for    and  <math>\widehat{b}</math>  are:
 
::<math>\hat{a}=\overline{x}-\hat{b}\overline{y}=\frac{\underset{i=1}{\overset{N}{\mathop{\sum }}}\,{{x}_{i}}}{N}-\hat{b}\frac{\underset{i=1}{\overset{N}{\mathop{\sum }}}\,{{y}_{i}}}{N}</math>
 
:and:
 
::<math>\hat{b}=\frac{\underset{i=1}{\overset{N}{\mathop{\sum }}}\,{{x}_{i}}{{y}_{i}}-\tfrac{\underset{i=1}{\overset{N}{\mathop{\sum }}}\,{{x}_{i}}\underset{i=1}{\overset{N}{\mathop{\sum }}}\,{{y}_{i}}}{N}}{\underset{i=1}{\overset{N}{\mathop{\sum }}}\,y_{i}^{2}-\tfrac{{{\left( \underset{i=1}{\overset{N}{\mathop{\sum }}}\,{{y}_{i}} \right)}^{2}}}{N}}</math>
 
:where:
 
::<math>{{y}_{i}}={{\Phi }^{-1}}\left[ F(T_{i}^{\prime }) \right]</math>
 
:and:
 
::<math>{{x}_{i}}=T_{i}^{\prime }</math>
 
and the  <math>F(T_{i}^{\prime })</math>  is estimated from the median ranks. Once  <math>\widehat{a}</math>  and  <math>\widehat{b}</math>  are obtained, solve Eqn. (xlineln) for the unknown  <math>y</math> , which corresponds to:
 
::<math>y=-\frac{\widehat{a}}{\widehat{b}}+\frac{1}{\widehat{b}}x</math>
 
Solving for the parameters from Eqns. (bln) and (aln) we get:
 
::<math>a=-\frac{\widehat{a}}{\widehat{b}}=-\frac{{{\mu }'}}{{{\sigma }_{{{T}'}}}}</math>
 
:and:
 
::<math>b=\frac{1}{\widehat{b}}=\frac{1}{{{\sigma }_{{{T}'}}}}\text{ }</math>
 
The correlation coefficient is evaluated as before using Eqn. (RHOln).
 
'''Example 3:'''
{{Example: Lognormal Distribution RRX}}

Latest revision as of 09:01, 9 August 2012

Redirect to:

Retrieved from "https://www.reliawiki.com/index.php?title=Template:Lognormal_distributionrank_regression_on_x&oldid=30741"