*! version 1.0.0 16Jul2023

Title

maxwell -- Maxwell's random error (RE) coefficient of agreement between 2 raters for binary data

Syntax

Using data stored in memory

maxwell rater1 rater2 [if] [in] [, tab]

Immediate form of maxwelli

maxwelli #a #b #c #d [, tab]

Immediate form of maxwelli referring to a saved 2 X 2 matrix

maxwelli matname [, tab]

#a: (rater1 = 1 and rater2 = 1); #b: (rater1 = 1 and rater2 = 0);
#c: (rater1 = 0 and rater2 = 1); #d: (rater1 = 0 and rater2 = 0).
#a, #b, #c, and #d must all be positive integers.

tab display 2 X 2 contingency table

Description

maxwell computes Maxwell's random error (RE) coefficient of agreement between 2 raters on a binary variable (Maxwell 1977). The RE coefficient measures the excess
of agreement over disagreement between two raters. It is attractive because of the weak assumptions in its derivation: doubtful cases are resolved in a truly random way
without reference to prior probabilities of incidence, and allowance is made for the possibility that a, the probability of agreement between raters, may differ
from cases in which an outcome is positive to those in which it is negative (Maxwell 1977).

maxwelli is the immediate form of maxwell; see immed.

Options

tab requests that the data be displayed in a 2 X 2 contingency table with both column and row percentages presented.

Examples

Using data stored in memory

. use maxwell.dta

. maxwell rater1 rater2

. bootstrap re = r(maxwell), reps(1000): maxwell rater1 rater2

Entering values manually using maxwelli

. maxwelli 13 3 2 12

. maxwelli 13 3 2 12, tab

Referring to a matrix using maxwelli

. matrix input B = (13 3\2 12)

. maxwelli B, tab

Stored results

maxwell and maxwelli store the following in r():

Scalars

r(ntar) number of targets (observations)

r(nrat) number of raters (will always be two)

r(maxwell) Maxwell's RE coefficient

References

Maxwell, A. E. 1977. Coefficients of agreement between observers and their interpretation. British Journal of Psychiatry 130: 79-83.

Citation of maxwell

maxwell is not an official Stata command. It is a free contribution
to the research community, like a paper. Please cite it as such:

Linden, Ariel (2023). MAXWELL: Stata module for computing Maxwell's random error (RE) coefficient of agreement between 2 raters for binary data

Author

Ariel Linden

President, Linden Consulting Group, LLC

alinden@lindenconsulting.org

http://www.lindenconsulting.org

Also see

Online: kappa, kappaetc (if installed)