Figure 1. Differences in yields (Mg ha^–1) for two barley (Hordeum vulgare L.) cultivar pairs, CDC Dolly–Harrington and AC Metcalfe–Harrington, evaluated at 18 sites across Alberta under three linear models (fixed-, mixed-, and random-effect models). The dashed lines represent upper and lower bounds (based on interaction-wise criterion) beyond which significant cultivar differences are indicated.