WINSTEPS will operate with a minimum of two observations per item or person, or even 1 observation with anchoring. This is useful for producing score tables with anchored items and dummy response strings. For statistically stable measures to be estimated, 30 observations per element (item or person) are needed: www.rasch.org/rmt/rmt74m.htm

 

The maximum number of reportable persons is 9,999,999 persons. The maximum number of items (NI=) is 65,000 items.

 

There can be up to 255 ordinally numbered categories per item (polytomies, rating scales, partial credit etc.).

 

The widest logit range of measures that maintains computational precision is 90 logits, but useful results can be reported with a measure range up to 700 logits wide.

 

Example: a dataset of almost 500,000 persons and 20,000 items was analyzed with Winsteps. The data were 99% missing. This type of analysis takes several hours, depending on your computer hardware.