Primary sources - Scientific experiments

Scientific experiments

The scientific method involves making an investigation to establish factual information. Its origins are in making careful observations of different phenomena in the natural world.

The scientific method involves testing a hypothesis, which is a statement about a phenomenon. The statement is based on prior knowledge and is an ‘educated guess’ about the relationship between factors influencing an observed phenomenon.

Factors that influence a phenomenon are called variables. A scientific experiment is a test specifically designed to investigate the nature of the influence of a single variable on the phenomenon.

The phenomenon is the dependent variable and the factor influencing it is the independent variable. A single experiment is only valid if it tests the effect of just one dependent variable against one independent variable, so making it a ‘fair’ test. Both variables need to be measurable, as far as possible using quantitative measures.

An experiment may prove or disprove a hypothesis. Either outcome is equally positive. If a hypothesis is disproved, the scientist will analyse and evaluate the results, construct a modified hypothesis and conduct a further experiment to test it. Scientists may pose a hypothesis that requires knowledge and understanding of a whole range of factors or variables. The scientists break up the main hypothesis into individual hypotheses and investigate a single pair of variables for each of these in turn so that the main hypothesis is not fully tested until a series of experiments is completed.

Human beings are complex organisms and their behaviour and physiological responses are influenced by very many variables. Ethical considerations mean that researchers have very limited scope to control these variables, as expected in a scientific experiment.

While experimental work is used in some psychology research, much other social science research can only be based on scientific principles as far as is permissible within ethical frameworks. Sometimes the research strategy mixes scientific method and social research.

For example, an investigation of the effect of an exercise routine on individuals’ health could measure some aspects (e.g. changes in pulse rate, respiration rate, blood pressure, etc.) under scientific conditions but would then have to adopt a social science methodology, such as a questionnaire, to investigate how the exercise made the individuals feel about their health.


Produce a table outlining the strengths and weaknesses of using scientific experiments to gather data. Include examples of when you should or shouldn't use experiments to gather information in different research areas (e.g. suitable for a chemical reaction)

Last modified: Monday, 30 Mar 2020, 14:19