Evidence in science
Evidence is what you observed or measured, and it counts even when it disagrees with what you expected.
A worked example
To test whether more light grows taller plants, change only the light. Keep the water, soil and pot size the same, then measure and record every plant.
The mistake people actually make
"The plant grew 4 cm this week" is an observation; "this plant is the nicest" is an opinion. Results that contradict your prediction get reported, not adjusted.