Experimental Design

Independent Variable

variable controlled by the researcher

Dependent Variable

- variable that may change in response to change in IV
- variable measured/observed

Controlled Variable

- variable kept constant during the investigation

Primary Source

- created by person directly involved in investigation

Secondary Source

- synthesis, review or interpretation of primary sources

Precision

- values close in agreement
- minimise random errors

Accuracy

- values close to true value
- increase accuracy by minimising systematic errors

Measurement error

- difference between true value and measured value

Systematic Error

- produces constant bias in a measurement that cannot be eliminated by repeating the measurement

Random Error

- Follow no regular pattern
- can be reduced by taking multiple measurements and then calculating mean
- can be reduced by refining measurement technique

Repeatability

consistency of the results when the experiment is repeated many times

Reproducibility

- closeness of the agreement between measurements of the same quantity, carried out under changed conditions of measurements.
- reproducible if similar results are obtained by different operators in different laboratories

Validity

whether an experiment or investigation is testing the set hypothesis and aims