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# st: Quick question of using -concord- to investigate proportional errors

 From cecilia sam To statalist@hsphsun2.harvard.edu Subject st: Quick question of using -concord- to investigate proportional errors Date Thu, 19 Jan 2012 13:29:18 +1300

```Hi all,

I am new to statistics and Stata, and need help for using -concord- in
Stata 11.0 for Windows.

I am comparing two datasets derived from 2 different methods. I
natural log transformed both datasets on the original scale, and typed
-concord y x, loa(regline)-. The output provides the slope of the
regression line, and a p-value listed besides the Pearson r (I
attached a part of the Stata output and attached below). Is this the
p-value that indicate the signficance of the slope of the regression
line?  In this case, does the p-value <0.05 mean that there are
statitically signficant proportional errors ?

Pearson's r =  0.271  Pr(r = 0) = 0.002  C_b = rho_c/r =  0.966

Reduced major axis:   Slope =     1.301   Intercept =    -2.727

Difference = y - x

Difference                 95% Limits Of Agreement

Average     Std Dev.             (Bland & Altman, 1986)

---------------------------------------------------------------

0.010       0.333                 -0.643      0.663

Correlation between difference and mean = 0.266

Thank you very much.
Regards,
Cecilia

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