3P.10—Planning investigations

A useful plan states a testable hypothesis, identifies the independent and dependent variables, chooses a measurable method and predicts the pattern that would support the hypothesis.

Specify the range and repeats, control relevant variables, choose a sample that represents the question, and decide how results will be recorded and analysed before collecting data.

“Increasing calcium concentration increases seedling mass” is testable when seedlings are matched for age and light, broths differ only in calcium, and mass change is measured after the same time.

A prediction is not a conclusion. A plan must also state how a result could contradict the hypothesis and how confounding variables would be detected.