• you might be asked to find the IV and DV —>

Variables

• Independent variable - the factor that is changed in the experiment (investigation)

• Dependent variable - measured variable that changes as a result of the independent variable

• Controlled variable - factors that must be constant to ensure a valid experiment

• Control experiments - experiment with the independent variable removed to ensure that the dependent variable is changing because of the IV not by other variables

  • For example, when testing for drugs, a certain group should be a taking a placebo

• You might be asked to explain or increase the accuracy, validity, reliability —>

Accuracy

• The difference between actual and measured values, the higher the difference the lower the accuracy and vice versa
• Accuracy is increased by changing the measuring method, using more sensitive measuring equipment

Validity

• How accurately a method measures what it is intended to measure
• Validity is increased by keeping all the other variables the same to ensure a fair test (controlled variables)

Past paper question

Explain what is meant by the term ‘valid results’ (3 marks)

• Valid results measure what they are supposed to
• There is no observer bias
• All variables apart from the IV have been controlled