### 15.17 RELIABILITY

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

The `RELIABILITY` 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.