SPSS Macro to calculate Krippendorff's alpha for nominal level, 2 category variables with 2 coders, with detailed printing

 

 

*----------------------------------------------------------------.

* This macro for SPSS for Windows calculates Krippendorff's .

* alpha for one or more nominal level variables that cannot be .

* skipped by coders and for which there are *two* valid coding .

* categories (0 and 1). In the process it prints the details .

* of the calculations (another version without the detailed .

* printout is available as well).

* If you have questions please contact Matthew Lombard at .

* lombard@temple.edu.

*----------------------------------------------------------------.

 

*----------------------------------------------------------------.

* To invoke this macro, start the SPSS program, use the File .

* menu to open a new syntax window. Paste the macro into the .

* new syntax file. Search for the text "FOR UNIT NO.:" .

* and following it type in the name of the variable in .

* your dataset that indicates the case or unit number.

* At the bottom of the file add the command to invoke the

* macro. Use this format: .

* .

* macroname vara varb.

* .

* where macroname is the name of the macro (which follows .

* the define command), vara is the dataset variable that .

* contains the values from the first coder, and varb is .

* the dataset variable that contains the values from the .

* second coder (an example has been included in this file).

* Multiple variables can be evaluated in a single use of the macro.

* .

* Use the "Run" menu option to have SPSS implement the macro.

*----------------------------------------------------------------.

*----------------------------------------------------------------.

 

*----------------------------------------------------------------.

* Define the macro and the variables to be used in the .

* macro, which are to be specified when the macro is invoked.

*----------------------------------------------------------------.

 

DEFINE K2C2CTP (!POSITIONAL !TOKENS(1)/

!POSITIONAL !TOKENS(1) )

 

*----------------------------------------------------------------.

* Save current SPSS environment settings, save a copy of the .

* current data-set file, and set default values for calculations .

* that follow.

*----------------------------------------------------------------.

 

SAVE OUTFILE= 'K2_TMP1.SAV'.

EXECUTE.

COMPUTE BRKGRP = 1.

 

 

*---------------------------------------------------------------------.

* COUNT NUMBER OF TIMES EACH CATEGORY WAS CODED .

* FOR EACH RECORDING UNIT: .

*---------------------------------------------------------------------.

 

COUNT N_1 = !1 !2 (0).

COUNT N_2 = !1 !2 (1).

PRINT /

/"FOR UNIT NO.: " CASENO " - N_1: " N_1

/"FOR UNIT NO.: " CASENO " - N_2: " N_2

/.

EXECUTE.

*---------------------------------------------------------------------.

* COMPUTE NUMERATOR VALUE: FIRST FOR EACH UNIT SEPARATELY.

*---------------------------------------------------------------------.

 

COMPUTE NUM =

(N_1 * N_2).

PRINT /

/"FOR UNIT NO.: " CASENO " - NUM: " NUM

/.

EXECUTE.

*---------------------------------------------------------------------.

* COMPUTE and save in a new temporary file the numerator value .

* across recording units.

* .

* NUMER is the sum across values of num all cases.

* NA_1 is the sum across all values of N_1 for the denominator.

* NA_2 is the sum across all values of N_2 for the denominator.

* UNITS is the number of cases.

*---------------------------------------------------------------------.

 

AGGREGATE

/OUTFILE=' K2_TMP2.SAV'

/PRESORTED

/BREAK=BRKGRP

/NUMER=SUM(NUM)

/NA_1=SUM(N_1)

/NA_2=SUM(N_2)

/UNITS=N.

GET FILE ' K2_TMP2.SAV'.

 

PRINT /

/"NUMER: " NUMER

/"NA_1: " NA_1

/"NA_2: " NA_2

/"UNITS: " UNITS

/.

EXECUTE.

COMPUTE DENOM =

(NA_1 * NA_2).

PRINT /

/"DEMON: " DENOM.

EXECUTE.

DO IF DENOM = 0.

COMPUTE RELIAB = 1.00 .

ELSE.

COMPUTE RELIAB =

(1) - ( ( (UNITS * 2-1)/(2-1) ) * (NUMER/DENOM) ).

END IF.

PRINT /'***************************************************'

/'KRIPPENDORFFS ALPHA FOR THIS VARIABLE IS: ' RELIAB

/'***************************************************'

/.

EXECUTE.

 

GET FILE 'K2_TMP1.SAV'.

EXECUTE.

 

ERASE FILE 'K2_TMP2.SAV'.

EXECUTE.

 

!ENDDEFINE.

 

 

K2C2CTP var1c1 var1c2.