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15.15 RELIABILITY

     RELIABILITY
             /VARIABLES=var_list
             /SCALE (name) = {var_list, ALL}
             /MODEL={ALPHA, SPLIT[(n)]}
             /SUMMARY={TOTAL,ALL}
             /MISSING={EXCLUDE,INCLUDE}

The RELIABILTY command performs reliability analysis on the data.

The VARIABLES subcommand is required. It determines the set of variables upon which analysis is to be performed.

The SCALE subcommand determines which variables reliability is to be calculated for. If it is omitted, then analysis for all variables named in the VARIABLES subcommand will be used. Optionally, the name parameter may be specified to set a string name for the scale.

The MODEL subcommand determines the type of analysis. If ALPHA is specified, then Cronbach's Alpha is calculated for the scale. If the model is SPLIT, then the variables are divided into 2 subsets. An optional parameter n may be given, to specify how many variables to be in the first subset. If n is omitted, then it defaults to one half of the variables in the scale, or one half minus one if there are an odd number of variables. The default model is ALPHA.

By default, any cases with user missing, or system missing values for any variables given in the VARIABLES subcommand will be omitted from analysis. The MISSING subcommand determines whether user missing values are to be included or excluded in the analysis.

The SUMMARY subcommand determines the type of summary analysis to be performed. Currently there is only one type: SUMMARY=TOTAL, which displays per-item analysis tested against the totals.