Repair the comparison — response practice

Stage-separated edition · 2 November 2026

Subtraction does not fix a confound

Same 20 minutes in a 22°C room; cups, lids and method match. Sleeve and mass differ.

Equal starts, unequal masses

Constructed teaching data: these values were invented for this activity, not collected in an experiment.

Setup

Mass (g)

Start (°C)

Final (°C)

Sleeve H

60

10

17

Sleeve J

120

10

15

1. Find both changes. Can the lower increase isolate a sleeve effect? Repair the comparison.