SIGN Subcommand (NPAR TESTS command) 

NPAR TESTS SIGN=varlist [WITH varlist [(PAIRED)] ]

SIGN tests whether the distribution of two paired variables in a two-related-samples test is the same. The output includes a Frequency table, showing, for each pair, the number of positive differences, number of negative differences, number of ties, and the total number. The output also includes a Test Statistics table, showing the Z statistic and two-tailed probability.

Syntax

  • The minimum specification is a list of two variables.
  • Variables should be at least at the ordinal level of measurement.
  • If keyword WITH is not specified, each variable in the list is paired with every other variable in the list.
  • If keyword WITH is specified, each variable before WITH is paired with each variable after WITH. If PAIRED is also specified, the first variable before WITH is paired with the first variable after WITH, the second variable before WITH is paired with the second variable after WITH, and so on. PAIRED cannot be specified without WITH.
  • With PAIRED, the number of variables that are specified before and after WITH must be the same. PAIRED must be specified in parentheses after the second variable list.

Operations

  • The positive and negative differences between the pair of variables are counted. Ties are ignored.
  • The probability is taken from the binomial distribution if 25 or fewer differences are observed. Otherwise, the probability comes from the Z distribution.
  • Under the null hypothesis for large sample sizes, Z is approximately normally distributed with a mean of 0 and a variance of 1.

Example

NPAR TESTS SIGN=N1,M1 WITH N2,M2 (PAIRED).
  • N1 is tested with N2, and M1 is tested with M2.