Experiments in Sociology – An Introduction

Last Updated on October 9, 2026 by Karl Thompson

An experiment measures the effect of one thing on another by changing one variable and keeping everything else the same. The variable the researcher changes is the independent variable (the cause); the variable they measure is the dependent variable (the effect).

This post covers:

1. A definition of an experiment, and its key features
2. The key terms: hypothesis, independent, dependent and extraneous variables, experimental and control groups
3. A worked example (tomatoes, naturally)
4. The three types of experiment: laboratory, field and the comparative method
5. The general strengths and limitations of the experimental method, and why sociologists rarely use it
6. Summary revision tables for laboratory and field experiments
7. A classroom starter for teachers: the two-stage balloon rocket

Experiments are part of the research methods component of A-level sociology, examined mainly on Paper 3 and also on Paper 1. You also need the logic of the scientific method for the theory side of the course, particularly the debate about whether sociology can be a science.

What is an experiment?

The aim of an experiment is to establish a cause and effect relationship between two variables. To do that, the researcher:

1. changes the independent variable,
2. measures what happens to the dependent variable, and
3. keeps every other variable the same, so that nothing else can explain the result.

That gives the experiment its three key features: control over variables, precise measurement, and the ability to establish cause and effect.

Experiments – key terms

Hypothesis – a specific, testable prediction about the effect one variable will have on another, made before the experiment as a starting point for investigation. For example: “tomato plants grown at 20 degrees will produce more tomatoes than plants grown at 15 degrees.”

Independent variable – the variable the researcher changes, to see what effect it has. The possible cause.

Dependent variable – the variable the researcher measures, which may be affected by the independent variable. The possible effect.

Extraneous variables – any other variables that could affect the dependent variable but are not what is being tested. The researcher has to control them, usually by keeping them the same for everyone, or the result can’t be trusted.

Experimental group – the group exposed to the change in the independent variable.

Control group – a group as similar as possible to the experimental group, which does not experience the change. Comparing the two shows the effect of the independent variable.

A worked example: the tomato experiment

It is easiest to see how an experiment works with an example from the natural sciences.

Say your hypothesis is that tomato plants grown at 20 degrees will produce more tomatoes than plants grown at 15 degrees. You take two plants of the same variety and grow them in the same greenhouse, with the same soil, light, water and nutrients — those are your extraneous variables, held constant. You put one plant on a heat pad set to 15 degrees and the other on one set to 20 — temperature is your independent variable. You pick all the tomatoes from both plants on the same day and weigh them — weight of tomatoes is your dependent variable.

Repeat it enough times to be sure the result wasn’t a fluke, and you can say whether the evidence supports your hypothesis, and by how much the higher temperature increases the yield. You can then refine the hypothesis — would 25 degrees do even better? — and test that.

Notice the order: the hypothesis comes first, and the experiment tests it. A hypothesis is never worked out from the results it is then used to test.

For the full version, including what the laboratory gives you and why the same thing is so hard to do with people, see the worked example in Laboratory Experiments in Sociology.

Experiments and objectivity

Experiments are supposed to produce objective knowledge: findings about cause and effect that exist independently of the researcher, uninfluenced by their values or opinions. The test of this is replication. If someone else repeats the same experiment and gets the same results, we can be fairly confident the results reflect something real rather than the person who ran it.

This is why Positivists see the experiment as the ideal scientific method, and why the question of whether sociology can use experiments is tied up with the question of whether sociology can be a science.

The tomato example isn’t idle, by the way. Nearly everyone eats tomatoes, so there is a lot of money in knowing exactly which combination of temperature, light, soil and variety produces the most tomatoes for the least cost — and I imagine an enormous amount has been spent finding out. That knowledge is what lets a grower set up a greenhouse and predict a harvest with some certainty.

The three types of experiment

Laboratory experiments take place in an artificial, controlled environment set up by the researcher. Control is at its highest, but the setting is unrealistic. See Laboratory Experiments in Sociology, which covers Milgram, the Bobo doll study and others.

Field experiments take place in a real social setting, such as a school, a workplace or a street, usually without the participants knowing they are being studied. They are more realistic but give the researcher less control. These are the type sociologists use most. See Field Experiments in Sociology, with seven examples.

The comparative method is not really an experiment at all, in that the researcher changes nothing. Instead, they compare two or more groups or societies that are similar in some ways and different in others, and look for correlations between the differences and some outcome. Durkheim’s study of suicide is the classic sociological example, comparing suicide rates across groups with different levels of social integration.

Strengths of the experimental method

Experiments are the best method available for establishing cause and effect, because only an experiment controls the other variables that might explain a result.

They allow precise measurement of the relationship between variables, which means accurate predictions about how they will interact in future.

The researcher can stay detached from the research, so the knowledge produced is more likely to be objective.

They have high reliability, because the conditions can be repeated exactly and the results checked.

Limitations: why sociologists rarely use experiments

Why the method may not suit studying society as a whole, or even individual people…

There are too many variables in the real world to control and measure them all.

Most social groups are too big. You can’t get a city into a laboratory to control all its variables, and you couldn’t even do it with a field experiment.

Many sociological variables can’t be changed. A researcher cannot assign people a social class, an ethnicity or a gender, and these are the variables sociology is mostly about.

People are not tomatoes. Human beings have their own reasons for acting, which often they don’t fully know themselves, so it is very hard to measure them objectively. They are conscious: they don’t just react in a predictable way to external stimuli, they think about what is happening, make judgements and act accordingly. Interpretivists argue that this makes the experimental method unsuitable for studying people at all.

Ethics. There are serious ethical concerns with treating humans as research subjects rather than as equal partners in the research — deception, consent and harm all come up repeatedly in the classic experiments.

The posts on laboratory and field experiments go through the practical, ethical and theoretical strengths and limitations of each type in full. In the exam, that is the level of detail you need: a general point about “experiments” earns far less than a specific one about a type of experiment, with an example.

Experiments at a glance: summary revision tables

If you’re revising, these four tables pull together the theoretical, practical and ethical strengths and limitations of laboratory and field experiments. The posts on laboratory and field experiments explain each point in full, with examples.

Laboratory experiments – strengths

	Strengths
Theoretical	Controlled conditions let researchers isolate variables and measure the exact effect of one thing on another.
	They can establish cause and effect relationships.
	They produce “objective” knowledge, helped by the high level of detachment between researcher and participant.
	Good reliability, because it is easy to replicate exactly the same conditions.
Practical	Easier to attract funding because of the prestige of science.
	They take place in one setting, so researchers can work like any other day job – no need to chase respondents.
Ethical	Participants usually know research is taking place (even if not its real purpose), and can be debriefed afterwards.
	Legality – lab experiments rarely ask participants to do anything illegal.
	The findings may benefit society – both Milgram and Zimbardo would claim their shocking findings outweigh the harm done to participants.

Laboratory experiments – limitations

	Limitations
Theoretical	They are reductionist: human behaviour cannot be explained through simple cause and effect relationships (people are not “puppets”).
	They lack external validity – the artificial environment is so far removed from real life that the results tell us little about how people would act outside the lab.
	The Hawthorne effect may reduce validity further – people may act differently just because they know they are in an experiment.
	They are small scale and so unrepresentative.
Practical	It is impractical to study large-scale social processes in a laboratory – you can’t get whole towns, let alone countries, into one.
	Time – small groups mean running experiment after experiment to build up a large sample.
Ethical	Deception and lack of informed consent – it is often necessary to deceive participants about the true purpose so they don’t act differently. Links to the Hawthorne effect.
	Some experiments have harmed participants – Milgram’s, for example.
	Interpretivists may be uncomfortable with the unequal relationship between researcher and participant – the researcher is the expert who decides in advance what is worth knowing.

Field experiments – strengths compared with laboratory experiments

	Strengths
Theoretical	Better external validity, because they take place in normal, real-world social settings.
	Less Hawthorne effect if participants don’t know they are being studied.
Practical	Larger-scale settings – field experiments can be done in schools or workplaces, so you can study larger social processes, which isn’t possible in a laboratory.
	A researcher can set up a field experiment, let it run for a year, and come back later.

Field experiments – limitations compared with laboratory experiments

	Limitations
Theoretical	It isn’t possible to control variables as closely as in a laboratory – you can’t observe participants 100% of the time.
	Weaker reliability – it is harder to replicate the exact context of the research.
	The Hawthorne effect (or experimental effect) may still reduce validity where participants know they are being studied.
Practical	Access is likely to be more of a problem with field experiments than with lab experiments – schools and workplaces may be reluctant to let researchers in.
Ethical	As with lab experiments, people are often not told an experiment is taking place so that they act naturally – so deception and lack of informed consent apply here too, as does the risk of harm. Often worse than in the lab, because participants may never be debriefed.

For teachers: the two-stage balloon rocket starter

The concepts above can be heavy going as an opening lesson. A two-stage balloon rocket makes a good alternative starter: it introduces dependent and independent variables, cause and effect, controlled conditions and making predictions before any of the terms are named. Students enjoy getting their hands on something, too, and there’s precious little opportunity for that in the rest of the A-level specification, so you may as well get it in while you can.

1. Set up the two-stage balloon rocket along a wire before the students come in, with only a little air in the balloons, so that it is deliberately a bit naff on its first run.
2. Ask students to discuss what they think will happen when you release it.
3. Release the balloon.
4. Discuss why it didn’t work very well.
5. Get the students to redesign the experiment.
6. Run round two.
7. Use “how far or how fast the rocket travels” as the dependent variable and “amount of air (fuel)” as the independent variable when you introduce the terms in the next stage (excuse the pun) of the lesson.

Questions you might get the students to consider:

• Which variables had the biggest impact on how far the rocket travelled?
• Did any variables have a very small impact, or none at all?
• With more time or other materials, what would you change to make the rocket travel even further?

Theory and Methods A Level Sociology Revision Bundle

Theory and Methods A-level sociology revision bundle cover

If you like this sort of thing, then you might like my Theory and Methods Revision Bundle – specifically designed to get students through the theory and methods sections of A-level sociology papers 1 and 3.

Contents include:

1. 74 pages of revision notes
2. 15 mind maps on various topics within theory and methods
3. Five theory and methods essays
4. ‘How to write methods in context essays’

Signposting and Related Posts

This post has been written primarily for students studying research methods as part of the AQA’s A-level sociology course.

After this introduction, most students study the two main types of experiment in turn: Laboratory Experiments in Sociology and Field Experiments in Sociology.

For the famous studies, see Milgram’s Obedience Experiment, the Bobo doll experiment and the Stanford Prison Experiment.

For everything else on this topic, see the main research methods page.

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