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Experimental Method

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Experimental Method

A key aim of psychology is to learn and understand more about psychological phenomena. This is usually done through a process called the experimental method. The experimental method in psychology research attempts to investigate the cause-and-effect relationship between variables. The crucial aspect of the experimental method is that it follows a 'scientific routine' to increase the chances of establishing valid and reliable results. As you can expect with all kinds of research, there are many advantages and disadvantages of the experimental method in psychology research.

The experimental method is a research process that involves following scientific guidelines to test hypotheses and establish causal relationships between variables.

  • To begin with our learning of the experiment method, we will start with a quick recap covering the elements that make up research.
  • We will then move on to discuss the experimental method in psychology research.
  • To finish off, we will discuss the advantages and disadvantages of the experimental method in psychology.

the experimental method, women observing chemical reaction occuring in a test tube she is holding whilst being surrounded by a desk with a laptop microscope and test tubes and a conical flask with chemical substances in them, StudySmarterFor research to be established as following the scientific method, the findings need to be observable after carrying out research in a carefully planned manner, freepik.com/biscotto.design

Experimental Method of Research

Before we get into the experimental method in psychology research, let's take a quick look at what are the basic components that make up scientific research.

Hypotheses and variables

The hypothesis is an important component of research. The hypothesis is formed at the start of an experiment with the purpose of stating what the researcher expects to find in their study. The hypothesis is important because it is used to identify if the results support or negate psychological theories.

The hypothesis is a specific, testable statement about the expected outcomes after comparing two (or more) variables.

The hypothesis needs to state the variables being investigated in the research.

The independent variable (IV) is the variable that the researcher manipulates/ changes in their study. This is the variable that the researcher believes these changes in the IV will cause a change in the dependent variable (DV).

The DV is the variable that is being observed and measured. The DV is thought of as the effect that is caused by the changes in the IV.

There are other types of variables, such as extraneous variables, participant variables and situational variables. These are variables that may cause changes in the DV. Ideally, psychology research that follows the scientific method should not have these types of variables. However, it is next to impossible to control for every potential variable that should not affect the DV.

Stages of the experimental method in psychology research

The experimental method has a standardised procedure and has several fixed steps to it that are usually carried out in a lab setting.

  1. Identify the topic of interest/research and form a hypothesis.
  2. Identify the IV(s) and DV(s), determine the design and type of experiment, and determine how to measure the IV and DV, e.g. self-report measure, observations, etc.
  3. Prepare the materials needed in the study and recruit participants through an appropriate sampling method.
  4. Conduct the experiment in a carefully planned scientific manner, collect the data and statistically analyse the results.
  5. Write up the lab report, evaluate the study and give suggestions for further research.

Experimental Method Example

A hypothetical study has been described below to show how the experimental method is used in psychology research.

  1. The researchers researched previously published work on the effects of caffeine on reaction times. The researchers hypothesised that drinking caffeine would affect reaction times based on the previous findings.
  2. The researchers identified reaction time as the DV and caffeine as the IV; they decided to carry out the study in a lab setting.
  3. The next stage involved preparing a test that measured reaction times, and participants were randomly assigned to three groups (drink with high levels of caffeine, drink with low levels of caffeine and no caffeine).
  4. The study was then carried out in a manner to prevent the reliability and validity of the study from being lowered.
  5. The results of the study were written up in the correct psychology format.

the experimental method, model of a brain with someone placing a lightbulb in it and three other people holding either a clipboard telescope or a smaller version of a lightbulb StudySmarterThere are several stages and requirements of research that follow the experimental method in psychology, freepik.com/pch.vector

The Features of the Experimental Method

There are three essential requirements of research that follows the experimental method.

  1. Empirical
  2. Reliable
  3. Valid

We will now discuss each of these and identify how researchers can try and make sure that their research meets these requirements.

Research needs to be considered empirical. Empirical research means that the findings should be reflective of objective facts that the researcher has observed rather than their subjective opinion.

The next requirement, reliability, is important as it makes sure that research findings are consistent across time, in different situations, settings and when applied to other people. When research is found to be reliable, then it is thought that the research findings are representative of the population and can be applied to real-life settings.

Reliability refers to how consistent the results of an experiment are. If the results are similar when the same procedure has been carried out on different occasions, settings or using different participants, then the findings will be considered reliable.

Testing the same study vigorously using the same methodology but on different days, settings, and times or using different samples is used to identify if a study is reliable.

The third requirement of research that follows the experimental method is validity.

Validity is how well a test measures what it intends to.

Validity is important because if the researcher is not in fact measuring what they claim they are measuring, then the results are not accurate and cannot be accurately interpreted or applied. For example, if a test claims it measures personality type but instead measures emotion level, it cannot be a valid test.

The researcher should ensure that their subjective opinion does not influence the research methodology and analysis to ensure research is valid. Researchers can try and combat this through:

  • Random allocation: Participants are randomly assigned to the experimental or control group; this is used to ensure that individual differences do not cause the results.

  • Single/Double-blind technique: The researcher is unaware of which experimental condition the participants are in. This prevents the researcher from giving subconscious hints that may influence the participants' behaviour.

Studies that do not use this may measure participants' artificial responses, so the results may not be considered valid.

the experimental method, five people standing in a row with speech bubbles above their head indicating their opinions, StudySmarterFor research to be established as valid, the study's methodology and analysis should not be influenced by the researcher's subjective opinion, freepik.com/rawpixel.com

Types of Experimental Method in Psychology: Experimental Designs

The allocation of participants in experimental/ control conditions is important to ensure that a study is valid. The experimental design is the different ways the participants are split into different conditions/groups of the IV. There are different types of experimental designs.

The independent group's design (IGD)

The IGD is when different participants are assigned to each condition.

When investigating the effect of sleep on reaction times, if using an IGD you would have one group with less sleep (4 hours) and one group with more sleep (11 hours), and the results between the two groups would be compared.

The advantages of this design are that it is less time-consuming than the alternative methods. As different participants are used for each condition there is less chance of participants guessing the hypothesis and altering their behaviour and order effects is not an issue.

However, the disadvantages of this design are that the researcher needs to recruit more participants compared to the other designs. Moreover, there is an increased chance of individual differences influencing the results.

The repeated measures design (RMD)

The RMD is when the same participants are used in all of the conditions.

RMD may be used when investigating if participants are better at memorising information from educational videos or from reading books. The study would involve testing memory after watching an educational video and after reading a book. Each participant would be tested in both conditions.

The advantages of this design are that individual differences will not influence the results of the study as each participant is tested in both conditions and fewer participants may be required to be recruited in comparison to IGD.

In contrast, a disadvantage of this design is that there is a higher risk of order effects influencing the results. This is the idea that the order of conditions tested may influence the study's results.

The matched pairs design (MPD)

The MPD is when participants in each condition are matched on specific variables relevant to the study, e.g. gender, age, IQ, etc.

The advantages of the MPD are that there is no chance of order effects since each condition has a different set of participants and there is less risk of individual differences affecting the results since participants have been matched on such variables.

The disadvantages of this design are that matching participants may be a difficult, costly and time-consuming process.

Advantages and Disadvantages of the Experimental Method in Psychology

Let's move on to discuss the advantages and disadvantages of the experimental method as a whole.

Advantages of the experimental method

  • The experimental method gives researchers a high level of control since they choose the IVs and DVs, how to measure them, and the procedure of the study. This means the studies are likely to be high in validity.
  • Because of the standardised procedures, experiments can be replicated and their reliability can be tested.
  • The experimental method allows cause and effect relationships to be determined, which is the goal of psychological research.
  • The conclusions of these experiments allow useful applications to the real world.

Disadvantages of the experimental method

  • Results are subject to human error and subjectivity, e.g. researcher bias, social desirability bias, order effects, etc and so it can be difficult to strictly adhere to the experimental method.
  • The procedure of the experimental method can be time-consuming and costly.
  • Can include practical problems, e.g. some variables may be hard to manipulate or measure.
  • Extraneous variables sometimes can't be controlled, which can lower the validity of a study and its results.
  • Participants' behaviour can be influenced by the researcher or the conditions of the experiment.

The Experimental Method - Key Takeaways

  • The experimental method is a research process that involves following scientific guidelines to test hypotheses and establish causal relationships between variables.
  • There are three important requirements of scientific research that follow the experimental method; these are that research should be empirical, reliable and valid.
  • The experimental designs used in psychology research are the independent measures design, repeated measures design and matched pairs design.
  • There are advantages and disadvantages of the experimental method in psychology.

Frequently Asked Questions about Experimental Method

The five steps of the experimental method are:


  1. Identify the topic of interest/research and form a hypothesis.
  2. Identify the IV(s) and DV(s), determine the design and type of experiment, and determine how to measure the IV and DV, e.g. self-report measure, observations, etc.
  3. Prepare the materials needed in the study and recruit participants through an appropriate sampling method.
  4. Conduct the experiment in a carefully planned scientific manner, collect the data and statistically analyse the results.
  5. Write up the lab report, evaluate the study and give suggestions for further research.

Some famous researchers who used the experimental method in psychology research are Loftus and Palmer's (1974) experiment on the accuracy of eyewitness testimony, Asch's (1951) Conformity study, and Milgram's (1963) Obedience experiment. 

The quasi-experimental method is similar to the experimental method in that it tests how changes in the independent variable affect the dependent variable. 


The difference between the two types of the experimental method is that quasi-experimental methods do not randomly assign participants to control and experimental groups, whereas the experimental method does.   

The experimental method is a research process that involves following scientific guidelines to test hypotheses and establish causal relationships between variables. 

The main advantages of the experimental method are:


  • The experimental method gives researchers a high level of control since they choose the IVs and DVs, how to measure them, and the procedure of the study. This means the studies are likely to be high in validity.
  • Because of the standardised procedures, experiments can be replicated, and their reliability can be tested.
  • The experimental method allows cause and effect relationships to be determined, which is the goal of psychological research.

  • The conclusions of these experiments allow useful applications to the real world.

Final Experimental Method Quiz

Question

What is the definition of the experimental method?

Show answer

Answer

The experimental method is a research process that involves following scientific guidelines to test hypotheses and establish causal relationships between variables. 

Show question

Question

What are the three main features of the experimental method?

Show answer

Answer

Research should be empirical, reliable and valid. 

Show question

Question

What does IV stand for, and what is its definition?

Show answer

Answer

Independent Variable (IV) - is the variable that the researcher manipulates/ changes in their study. This is the variable that the researcher believes these changes in the IV will cause a change in the dependent variable (DV). 


Show question

Question

What does DV stand for, and what is its definition?


Show answer

Answer

Dependent Variable (DV) - The DV is the variable that is being observed and measured. The DV is thought of as the effect caused by the changes in the independent variable. 


Show question

Question

What do extraneous variables affect? 

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Answer

Both

Show question

Question

Can a research be considered valid if many extraneous variables have been found to affect the study? 

Show answer

Answer

No

Show question

Question

What are the different techniques used to improve the validity of research? 

Show answer

Answer

  • Random allocation: Participants are randomly assigned to the experimental or control group; this is used to ensure that individual differences do not cause the results.
  • Single/Double-blind technique: The researcher is unaware of which experimental condition the participants are in. This prevents the researcher from giving subconscious hints that may influence the participants' behaviour.

Show question

Question

What is an independent group design?


Show answer

Answer

Independent groups design is when different participants are assigned to each condition.


Show question

Question

What is a repeated measures design?


Show answer

Answer

Repeated measures design is when a participant is tested in all of the conditions in the experiment.


Show question

Question

What is a matched pairs design?


Show answer

Answer

Matched pairs design is when participants in each condition are matched on specific variables relevant to the study, e.g. gender, age, IQ, etc., to another person who will be tested in the other condition.


Show question

Question

What are the disadvantages of the experimental method? 

Show answer

Answer

  • Results are subject to human error and subjectivity, e.g. researcher bias, social desirability bias, order effects, etc and so it can be difficult to strictly adhere to the experimental method.
  • The procedure of the experimental method can be time-consuming and costly.
  • Can include practical problems, e.g. some variables may be hard to manipulate or measure.
  • Extraneous variables sometimes can't be controlled, which can lower the validity of a study and its results.
  • Participants' behaviour can be influenced by the researcher or the conditions of the experiment.

Show question

Question

What are the advantages of the experimental method? 

Show answer

Answer

  • The experimental method gives researchers a high level of control since they choose the IVs and DVs, how to measure them, and the procedure of the study. This means the studies are likely to be high in validity.
  • Because of the standardised procedures, experiments can be replicated, and their reliability can be tested.
  • The experimental method allows cause and effect relationships to be determined, which is the goal of psychological research.
  • The conclusions of these experiments allow useful applications to the real world.

Show question

Question

Can the experimental method be used to identify if there is a cause-and-effect relationship between variables? 

Show answer

Answer

Yes

Show question

Question

What is a hypothesis? 

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Answer

The hypothesis is a specific, testable statement about the expected outcomes after comparing two (or more) variables. 

Show question

Question

Is it acceptable for research following the scientific method to be based on the researchers' subjective opinion? 

Show answer

Answer

No

Show question

Question

What are the five main steps of the experimental method?

Show answer

Answer

  1. Identify the topic of interest/research and form a hypothesis.
  2. Identify the IV(s) and DV(s), determine the design and type of experiment, and determine how to measure the IV and DV, e.g. self-report measure, observations, etc.
  3. Prepare the materials needed in the study and recruit participants through an appropriate sampling method.
  4. Conduct the experiment in a carefully planned scientific manner, collect the data and statistically analyse the results.
  5. Write up the lab report, evaluate the study and give suggestions for further research.

Show question

Question

What are the three different designs that can be used in the experimental method? 

Show answer

Answer

The independent measures design, repeated measures design and matched pairs design. 

Show question

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