35 = 3 + 7 + 12 + 8 + 5. Goal: watch the denominator change with category inclusion, then explain the source limit.
- 0–3: Put all 48 in view before touching the offline category filter or paper denominator mat.
- 3–10: Model All = 25/48≈52.1%; select Hatch+Ring = 23/36≈63.9%. The browser re-computes from fixed invented counts; it does not download or collect data.
- 10–22: Learners try two category selections, record numerator/denominator, compare the pattern-family pass proportions within this register and restore all categories. Ask which table entries did not change (all source cells); differing category rates do not identify a cause.
- 22–30: Routes: keyboard/screen-reader toggle and complete spoken status; tactile counter frames with labelled pattern cards; hand table/calculator. Digital Technologies evidence requires actual interactive analysis; paper maths evidence is equivalent for denominator reasoning.
- 30–35: Exit: “Did the filter change the source record?” Key: no, only the selected reference group. Move: draw a boundary around selected rows and recount.
Alternate domain: Invented fabric swatch layout categories. Optional/home: use paper only to compare two subsets; no device required.