Bland-Altman plot measure the agreement between two different methods which measures the same variable. As far as I understand Bland-Altman can measure only if the two methods have the same unit of measurement. I want to measure the agreement between two methods which measure the same variable (a continuous variable) but in different units, how can I proceed?

  • $\begingroup$ What do you mean by 'agreement' when the units differ? $\endgroup$
    – Glen_b
    Commented Sep 5, 2014 at 16:07
  • $\begingroup$ center and scale the variables (then they are 'unitless') ? $\endgroup$
    – user83346
    Commented Jul 22, 2016 at 6:27
  • $\begingroup$ Do the two measures evaluate the same thing? If yes it is easy. $\endgroup$ Commented Apr 24, 2017 at 2:33

1 Answer 1


just factor the units to the same unit? eg if one is in mg/L and another in µg/L, just factor both result sets down to µg/L (simply multiply the mg/L vector by 1000) and then do the comparison. If the units are especially or fundamentally different (ie like Bq/L vs ng/fortnight or something like that!) then im not sure how you would do the comparison, and even if you did, im not sure that it would yield any meaningful result.


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