Posted on: 4th May 2020

Experimental Research Design

An experimental research design is a  research design that helps in measuring the influence of the independent variable on the dependent variable. Experimental research is Quantitative methods along with a scientific approach in which a set of variables remains constant. An experimental research design requires creating a process for testing a hypothesis. Experimental design can also be referred to as a set of process designs for determining the relationship between variables. You to control experiment require:

  • A testable hypothesis
  • An independent variable which you can manipulate
  • One dependent variable which can be measured
Experimental Research Design

You to apply experimental research design in an effective manner need to have a good understanding of the system on which you are performing an investigation.

How to use experimental Research Design?

The 4 steps of using the experimental research design are:

Step 1: Defining Research Questions and variable

You need to consider research Questions. Researchers require spending time reading about related to your field of study. It is very much essential for you to address knowledge gaps. You need to identify questions that interest you.

Example Question 1: Phone use and sleep

Researchers intend to gather information about the use of phone before bedtime influence sleeping patterns. Particularly, you intend how the number of minutes a person utilizes their phone before sleep influence the number of hours.

Example 2: Soil respiration and temperature

An investigator performs research for analyzing the way temperature influence soil respiration

You need to define the main variables and make assumptions about the way they are related. It is also considered as the best tactic for translating research questions into an experimental hypothesis. Researchers can start performing experimental research by simply listing dependent and independent variables.

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Research Questions Independent variable Dependent variable
Use of phone and sleep Minutes phone is used by a person before going to sleep Number of hours person sleeps at night
Soil respiration and temperature Air temperature just above the soil surface Carbon dioxide respired from soil

After that, you are requiring to think about confounding variables. It is also very much important for you to consider the technique you are going to use for controlling confounding variables in an experiment.

Confounding variables Techniques to control it
Use of phone and sleep Natural variations in sleep patterns of people You can control confounding variables by controlling them statistically. The researcher is requiring measuring the average variations between using the phone before sleep.
Temperature and soil respiration Moisture in soil influences respiration. An increase in temperature may lead to a decline in decline in the moisture of the soil. Control experimentally:  You need to continuously monitor the moisture in the soil and you need to add water for maintaining the consistency.

At last, you need to integrate these variables and put them into a diagram. You can utilize arrows for demonstrating the relationship between variables. Researchers can also use signs for showing expected directions of the relationships.

About example 1 that is the influence of phone use on sleeping patterns. It has been found from the above that increase in the use of the phone has an adverse influence on hours of sleep. You can predict an unknown effect of natural variations on hours of sleep.

For example 2: the researcher has analyzed a positive correlation between soil respiration and temperature.

Step 2: Write a Hypothesis

At this step, you have a good conceptual understanding of the system you are studying. This is a step where you need to write a specific and testable hypothesis that addresses research questions.  You can ask people questions about how the rise in air temperature near the soil surface influence the amount of carbon dioxide respired from the soil.

Null hypothesis Alternative hypothesis
Use of phone and sleep The use of a phone before sleep does not correlate with the amount of sleep a person gets. An increase in the use of phones before sleeping leads to a decrease in sleep.
Temperature and soil respiration Air temperature Does not have any correlation with soil respiration. An increase in temperature results in an increase in soil respiration.

At the next step, you need to describe how to design a control experiment. To control experiments you should have the potential to:

Systematically and precisely manipulates the independent variable

Accurately measure the dependent variable

You need to control any potential; confounding variables.

In case, the research you are performing does not match with the above criterion, there are other types of research you can utilize for answering research questions.

Step 3: Designing experimental Treatments

At the time of performing experimental research, you need to understand that the way you are manipulating the independent variable can influence the external validity of the experiment.  External validity can be referred to as level up to which the outcome of results can be generalized and applies to the broader world.

Firstly, you need to decide the extent up to which you need to manipulate the independent variable.

About a Soil warming experiment

The researcher can decide for the increasing temperature of the air

  • Just a little bit above the natural range for the study region.
  • Over a wide range of temperatures to mimic future warming
  • Over an extreme range that is beyond possible natural variations.

Secondly, you are required to choose a level up to which you want to see variations in independent variables. You can make such a decision based on your experimental system.


You can decide on treating the use of the phone as:

  • A categorical variable, either as binary or level of factor
  • A continuous variable

Step 4: Assigning subjects to the treatment group

It is very much essential for you to properly apply experimental treatments for testing subjects, as these tactics will help you in generating highly valid and reliable research results. Before assigning the subject to the treatment group you need to do the following:

Firstly, you are required to think about the size of the study. You also are requiring a determining number of participants you want to include in your study. After that, you need to assign subjects on a random basis to treatment groups. It is also very crucial for you to make sure that every group receives a unique treatment.

You also need to include a control group that receives no treatment. It is a control group that will help you in determining what would happen to test subjects without any experimental interventions.

At the time of assigning subjects to groups, you are required to make a selection from different designs such as

  • Completely randomized designs Vs randomized block design
  • An independent measure design Vs repeated measures design

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You can completely randomize an experiment within a block:

In a completely randomized design, you need to assign each subject to a treatment group using a random sampling technique.

Randomized block design: You are requiring to group subjects as per their characteristics, after that you need to assign them to treatments by using the random sampling technique.

Completely Randomised design Randomized block design
Use of phone and sleep You need to assign subjects a level of use of the phone. You can use a random number generator. Firstly, you are requiring to group participants based on age and then you can assign them to the use of phone treatment by applying the random sampling technique.
Soil respiration and temperature Warning treatments are assigned to soil plots at random by utilizing a number generator map coordinates in the study area. You can group soil by average rainfall and after that you can assign treatment plots randomly.

In a few circumstances randomization techniques is not effective; therefore, the investigator designs partially random or non –random research design. An experimental study where treatments are not assigned randomly is known as a Quasi-Experimental design.

Independent Vs Repeated measures

In an independent measures design, a person or subject receives a single of the possible level of an experimental treatment. In the context of social and medical research, the Researcher sometimes utilizes matched pairs within an independent measures design for ensuring that every treatment group contains a similar variety of tests subjects in equal proportions.

Repeated measures design: All person or subjects in research receives every experimental treatment consecutively and researcher measure responses of all treatment. Repeat measures can also be defined as an experimental research design where influence takes place over time. Researchers also measure the response of people over time for measuring influence.

Counterbalancing includes randomization or reversing the order of treatments. The researcher uses counterbalancing in repeated measures research design for making sure that the order of treatment does not affect the outcome of the experiment.

Independent measure design Repeated measures design
Use of phone and sleep You need to assign subjects a level of phone use and then you are requiring to follow the level of phone use in your experiment. The researcher assigns subjects consequently to high, medium, and low levels of phone use throughout the experiment.
Temperature and soil Investigator assigns warming treatment to soil plots randomly. After that soil is kept at this temperature during the experiment. Each plot gets warming treatment during the treatment. On a random basis subjects receive treatment.


From the above article, it has been concluded that experiments are context-dependent.  Another fact which has been discovered is that a good experimental research design researcher has an in-depth understanding of the system which helps them in generating valid and reliable results.

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