Anthropogenic factors and Laboratory work 1

A laboratory experiment finds a causal link by changing one factor while keeping the others equal. It has an independent variable (for example light or the watering rate), a dependent variable (plant height, leaf count, colour) and a control group (normal conditions). Each variant uses several plants (replication), because the chance result of a single plant is unreliable. Measurements are taken at the same time and in the same way, results are put into a table, and the mean is calculated. For example, bean or wheat seeds can be grown in four cups: (1) light + normal watering (control), (2) light + little water, (3) dark box + normal watering, (4) dark + little water. Seedlings grown in the dark are pale, long and thin (etiolation) because chlorophyll does not form and the plant stretches toward light. The conclusion rests on the results and applies only to the factors studied.