What does x_{i} mean in SAS documentation of Wilcoxon Signed Rank Test when we have paired data

[pywils]

Wikipedia's entry on the Wilcoxon Signed Rank Test says that the test is "used to compare two related samples, matched samples, or repeated measurements." In contrast, The SAS documentation of the Wilcoxon Signed Rank Test references x_{i} (a data value) and its rank, r_{i} as though we only had a single variable. How do I interpret x_{i} from SAS' documentation when I have paired data?

Thank you!

[Reeza]

Usually when you have paired data, you take the difference and assume the difference is the single array. Its possible it's different in this case, but I suspect it's the same.

[StatDave · Accepted solution]

See the second paragraph on that documentation page. As described there, to perform the test to compare paired samples, you create a single variable that is the difference within each pair. The x_i are those differences and the r_ are the ranks.