How would you describe a scientific experiment

4. Presentation of the method

The experiment is a classic part of scientific research. In addition to its application in the empirical field, it can also be used as a teaching / learning method in many subjects of school teaching and further education. The exact course will, however, differ depending on the subject, depending on the area (scientific / humanities) in which the experiment is to be carried out.
In the natural sciences subjects, a classic experiment is recommended, in which the learners act as experimenters. These can be demonstration experiments, in which the aim is merely to present a theory and its statements or a method, or also (hypothesis) test experiments.
In the humanities subjects, experiments in the sense of empirical social research can also be carried out, in which the learners act as test supervisors and other learners or external persons serve as test subjects. However, depending on the experiment (as the examples below show), this type of experiment requires a certain degree of maturity and a sense of responsibility on the part of the experimenter towards the test subjects and is therefore mostly more suitable for older learners, for example in adult education or at the university.
Since the experiment fulfills different functions in each of the different subjects and can be carried out in different ways, we limit ourselves here to the presentation of the experiment in subject teaching and in empirical social research for the purpose of clarifying principles.

4.1 Example: the flowerpot sewage treatment plant

In order to make it clear what such an experiment could look like in the context of subject teaching in primary school, we are introducing the “flowerpot sewage treatment plant” at this point. The set-up of this experiment is about the students stirring different substances into water and then pouring these mixtures through flower pots filled with cleaning materials (cotton wool, sand, paper, earth). The pupils should use the water that escapes below to recognize which material is best for cleaning and which traces (smell, color) it leaves behind. Then there is still the option of distilling the purified water in order to make any residues visible.

4.2 The features of the experiment

Using this example, we would now like to briefly explain the characteristics of the school experiment according to Wagenschein.

  • Repeatability: There are several aspects to this characteristic. The results of the experiment must be repeatable at any time - with the condition that this reproduction is independent of the person. This point implies that the experiment in its planning and implementation must be so clearly interpreted that it is comprehensible to outsiders. In this way the learner looks for a witness for his perception of reality, someone who shares his point of view with him.
    In our example “flowerpot sewage treatment plant”, this characteristic can be found again as follows: If the learners compare their results with those of other pupils, they can see that they have found similar results. Another way to check the repeatability of the experiment is to be able to recreate the experiment at home and get the same results again.
  • Conservation: This characteristic means that none of the elements that are involved in the respective experiment are lost, but rather remain in any form. Learners know that the observed effect has a reason they want to find out. In the example of the flower pot sewage treatment plant, you can see the process of cleaning the water. The answer to the question of where the contaminants in the water have gone can be answered by yourself by examining the cleaning material and finding the various substances in it.
  • Order: Children observe their environment closely and try to sort the many impressions and experiences they have every day and to incorporate them into their previous knowledge. If the learners learn something new in class, observe something inexplicable and perhaps even inconsistent, they want to explain these impressions for themselves, for example by relating them to old information.
    In our example, the children can see that the contaminated water looks clear and clean again after it comes out of the flower pot. This is initially incomprehensible to the learners. However, if you carry out the experiment yourself, you will be able to draw connections between the water and the various cleaning materials and explain the phenomenon of water cleaning.

The course of the experiment in school lessons can also be assigned to Dewey's problem-solving scheme of action, as described above in the theoretical justification.


4.3 The phases of the experiment

An experiment runs in three phases, the planning phase, the implementation phase and the evaluation phase. Often the planning phase is decisive for the implementation, as it defines the further steps and thus the foundation for the success or failure of the experiment is laid here.
We will now first present the phases using the experiment in empirical research (in a simplified form) and then establish the respective references to the experiment in school.
On the basis of this comparison, we can finally show similarities or similarities or differences between these two types of experiments.

planning phase
Objective: The basis for applying an experiment is usually a scientific background that raises certain questions for the researcher. This means that an experiment is used by the researcher to solve a problem. The researcher is confronted with an unknown or surprising fact, which leads to the fact that he wants to learn more about this process. The first step here is the formulation of a precise question. This should contain a concrete statement about the goal of the experiment (what exactly do I want to find out?)

  • In the case of experiments in the context of school lessons, the first step is to consider how the learners can be introduced to the "experiment" form of learning. In science lessons, the discovery of new facts plays an important role for the learners. A starting point for the learners could be a phenomenon incomprehensible to them, which raises questions, may have puzzled, astonished or confused them. Self-initiated questions from the children can also be used as an introduction to experimentation, as can questions that an excursion into nature or a small model experiment by the teacher provokes. The result of all these different possibilities is that the learner's curiosity is aroused, that they begin to be interested in something and want to learn more about it. At this point it is important to take into account that the phenomenon to be investigated comes from the children's world of experience, i.e. specifically that the children have already had everyday experiences with the things they are supposed to investigate. In this way, skills that have already been learned during the experiment can be used to gain new insights, on the other hand they can complete the knowledge that is required in everyday life. The specific question about an experiment often emerges when the children look at a phenomenon that is inexplicable to them and express their suspicions and questions.

Factual hypotheses:

  • After these initial considerations, the researcher can develop his hypothesis according to the following rules: it must not contain any negations, should be formulated as a statement and not contradict each other.
  • In the experiment, the formation of hypotheses should be left to the learners as far as possible, who can think about the possible course of the experiment and try to assess and predict effects based on their previous experience with the materials. The teacher should give the learners the opportunity to formulate a hypothesis based on their ideas. The next step then includes the consideration of how the hypothesis could be tested, which materials are needed for it, who could take on which task, etc. The learners have become a small research group that pursues a goal and an explanation, for example for the processes in the Want to find nature.

Operationalization of the hypothesis:

  • The operationalization makes terms observable or measurable. The researcher must assign observable data to the behaviors or states of materials mentioned in the hypothesis in order to be able to guarantee the measurability of the various phenomena.
  • In class, the learners think about how they could measure the result of their experiment or compare it with other results. This could, for example, be a precise definition of the “clean” state for the water that is obtained at the end of the experiment - based on the initial experiment “sewage treatment plant”. At this point it must be clarified, for example, whether it is sufficient for the water to look clear again, or whether it should also smell and taste clean.


  • The results of the experiment relate to the effect of the various variables that can be changed by the researcher. Research can distinguish between three types of variables. The independent variables are changed by the experimenter according to the plan to ensure that their effect on the dependent variables to be able to determine. Depending on the complexity of the experiment, this variation can take place in two or more stages. The dependence of the last-mentioned variables on the independent variable is the actual subject of the study. Another variable that can shape the results is the so-called Disturbance variable. This includes all external influences that, in addition to the independent variables, have an influence on the object of investigation. The experimenter must also check these variables in order to be able to guarantee the unambiguousness of the results later.
  • The variables also play a role in the school experiment. The learners can exchange the various substances they are experimenting with for other materials, varying them in order to test the effect of this change on the remaining substances. In this type of experiment, as in empirical research, there is a dependent and an independent variable. We would like to clarify this briefly using the example of the “sewage treatment plant”. The water contaminated with color, which is given by the students through the different filters, represents the dependent variable, the pots with the different cleaning materials represent the independent variable. The students can filter part of the contaminated water through one material each and highlight the differences . The experiment can, however, also be carried out with different liquids and only one cleaning material, in which case the liquids act as the independent variable and the cleaning material as the dependent variable. Both the one and the other approach are recommended for this experiment, as all the effects that the variables have on one another can be observed in this way.


  • The scientific researcher must define his subject area and within it his measuring field. The researcher in empirical social research selects the test groups that are to take part in the experiment he is planning. At this point, he must consider who his research result should apply to and accordingly make his selection of test subjects, as these are representative of the target group. During the experiment, the researcher works with several groups, the number of which is based, for example, on the independent variables, in addition to an untreated control group.
  • In the school experiment, for example, the learners choose between different materials whose reaction to one another is to be researched. One substance A represents the dependent variable, two others the independent variables B and C. In the experiment, A and B are first mixed together, then A and C. In this case, the control group only consists of the untreated substance A.

Design of experiments:

  • The researcher is faced with the task of finding a suitable test situation in which the effect of the variables can be measured.
  • The learners consider specifically what they need for the implementation of the experiment, which materials could be particularly suitable or which additional requirements must be met for a good success. In the case of younger participants, the teacher should be particularly helpful at this point or explain the test procedure in detail. The exact procedure is then determined, either on the basis of a test plan prepared by the teacher or on the basis of the deliberations of the research group.

Implementation phase

This phase begins with the completion of various organizational tasks such as the selection of the test subjects, the test director or the premises. The experiment is then carried out according to the test plan and the investigator's observations are recorded.

  • In the subject lesson, the experimental material is first provided by the teacher, then the learners begin to set up the experiment. After completing these preparations, the experiment will be carried out according to plan. These first steps from the provision of the material to the implementation are recorded in writing by the learners, as these records are then incorporated into the evaluation, for example to provide information about possible errors during the experiment that could have contributed to the bias of the results. The individual observations made by the learners during the actual implementation must be precisely recorded. During an experiment, the students learn to recognize the relevant variables and can formulate if-then relationships. In addition, they have the opportunity to compare their own experiment with other experiments (for example those of their classmates) or with personal everyday experiences. For Wagenschein, “understanding” means “connecting”: The learners combine the new with the old, they create a relationship and expand their knowledge. While working in the group, social behavior and self-confidence are also trained, as the learners have to cooperate with the other group members on the one hand, but also want to express their opinion and assert their interests on the other.

Evaluation phase

In empirical research, the evaluation plan should be developed before the actual evaluation phase; the data is then evaluated according to previously established rules. However, there is a risk that a number of errors will creep in between planning and evaluation, which can lead to distorted results. These errors include, for example:

  • Meaning error: Only operationalizable phenomena are observed, which can have the consequence that other important processes are classified as unimportant. This leads to a rather meaningless research.
  • Planning errors: In order to avoid errors in planning, the researcher should take a break before starting the implementation and reconsider his project in order to be able to clarify possible unevenness in advance.
  • Instructional errors: These errors can arise if the test subjects are not fully prepared for the experiment.
  • Insulation failure: The “unnatural”, staged environment of many experiments can evoke various effects on the test subjects, which then lead to distorted results.
  • Over-generalization: The results, which are often only true for a small group of people, are carried over and generalized to too large a group.

In general, the results of experiments can be classified in three ways.On the one hand, there are those experiments, the results of which confirm the hypothesis set out in advance; on the other hand, there are those experiments in which the researcher was unable to determine the expected effects. In these experiments, the possibility must then be clarified whether the effects were there, but were overlaid by random influences, so that the researcher was not able to prove them. In some experiments, in addition to the expected side effects, the researcher did not take into account.

The results of the experiment are also saved and evaluated by the learners in class. Depending on the age of the students and the degree of difficulty of the respective experiment, the teacher can assist them with this work. In this phase, the learners are faced with various requirements, such as calculating mean values, recognizing meaningful relationships, deriving an end result through the interpretation of the individual results or comparing the results with the hypothesis (confirmed / not confirmed). According to Bruner's media theory, the securing of the results by the learners should take place in three steps:

  • inactive: this means that the learners deal actively with it during the course of the experiment
  • iconic: the results are recorded in writing and images; this can be done, for example, in the form of tables or sketches (e.g. using the test setup).
  • symbolic: the results are presented to the other groups


The role of the teacher and the learner

The role of the teacher

The role of the teacher is primarily characterized by his reluctance. Before the experiment begins, he makes the preparations, selects an experiment and possibly the associated material and then thinks about a suitable introduction to the topic with which he can get the learners in the mood for the experiment. During the actual implementation, he is available to the individual groups as a learning advisor, answers questions or gives support in case of problems.
The teacher should give his pupil the opportunity to have a say, to choose and to decide himself, but also to discuss things with other pupils and to become a team with them. All of this can only be achieved if the learners are viewed as independent individuals who are allowed to discover, ask and understand things without being influenced or even under pressure. Each individual must be encouraged individually, depending on their strengths and weaknesses, so that they can participate as an active member in the work of their group.
In general, the teacher should make sure that the experimental is not neglected in his teaching experiment and that the learners do not learn by heart purely reproductive, experiment by experiment, instead of trying out new methods and exploring new areas of knowledge themselves.

The role of the learner
The role of the learner is characterized by an interest in new issues that need to be discovered, as well as independence in learning and the ability to work together in groups and form a team. This implies that the impulse to conduct an experiment in class should come from them as well, if possible. The basis for this, however, must be created by the teacher by introducing the learners to the experiment method at an early stage and thus making it a natural part of the lesson.
The learners have to be able to get involved with new, as yet unanswered questions on a topic and learn to solve problems independently. This places high demands on their communication skills, which should continue to develop while working in a team, since joint results can only be found with a functioning exchange among each other.