How to Create an Experimental Design 06

How to Create an Experimental Design

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What is an Experimental Design?

How to Create an Experimental Design 07

Experiments are used to study causal relationships between variables. It involves manipulating one or more independent variables to identify and measure the degree of change in one or more dependent variables. 

An experimental design is an outline of the process that will be employed to study this causal relationship. It is a plan that addresses how the research will be carried out in a controlled and objective way in order to achieve useful and reliable results.

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Types of Experimental Design

There are three main types of experimental designs, namely: 

  • Pre-experimental Research Design: Generally conducted before a true experiment, where a small group of subjects are studied to identify a cause-and-effect relationship. This design is used to obtain insights on whether or not further investigation is worthwhile. 
  • True Experimental Research Design: The researcher employs random assignment to assign subjects to the treatment and control group. 
  • Quasi-experimental Research Design: The researcher employs non-random criteria to assign subjects to the treatment and control group. 

How to Create an Experimental Design

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Although different experimental designs will employ different processes and frameworks. In this article, we will specifically explore the steps that must be carried out to conduct a controlled experiment.

The following steps can be used to set up an experimental design:

    1. Define your Variables
    2. Create a Hypothesis
    3. Design Experimental Treatments to Manipulate the Independent Variable
    4. Assign Subjects to Groups
    5. Define how the Dependent Variable will be Measured

Define your Variables

The first step in creating your experimental design is to clearly define the independent and dependent variables relevant to your research question. 

For instance, let’s assume you want to measure the effect of water temperature on the rate at which salt dissolves. To design your experiment, you will have to identify your independent and dependent variables. In this case, they are: 

  • Independent Variable: Water temperature
  • Dependent Variable: Time it takes salt to completely dissolve in the water

In this step, you must also think about any extraneous and confounding variables that could influence the outcome of your study. By identifying these variables, you can think about how you want to control them so as to minimize or eliminate their influence on the relationship being studied between the independent and dependent variables. 

In this case, you will need to consider other variables that will affect the solubility of solids in liquids. This will include variables such as forces and molecular bonds, as well as pressure. These variables must be kept constant. 

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Create a Hypothesis

Once you’ve clearly defined your variables, you can write your hypothesis. Your hypothesis will illustrate how you expect the variables in your study to interact. 

Continuing with our example, this is what the hypothesis will look like: 

Null Hypothesis (H0): Water temperature does not correlate with the rate at which salt will dissolve in it.

Alternate Hypothesis (H1): Increasing water temperature will increase the rate at which salt dissolves in it. 

Design Experimental Treatments to Manipulate the Independent Variable

In the third step of designing your experiment, you must decide how you will manipulate your independent variable. The way you choose to do so can significantly affect the external validity of your study. 

Before you can select the best way to manipulate your independent variable, you must first decide how widely to vary it. In the case of water temperature, you can choose to vary it by 5 degrees, 10 degrees, or so on. You must then decide how finely to vary your independent variable. Let’s assume you decide to vary the water temperature by 1 degree. 

Assign Subjects to Groups

In this step, you must assign subjects to groups using random assignment. You may also choose to include a control group, which receives no treatment. A control group allows us to clearly attribute changes in the experimental group to the administration of the treatment. 

Define how the Dependent Variable will be Measured

The final step in your experimental design is to decide how you will measure your dependent variable. It is important to select a method of data collection that is reliable so as to minimize any bias. Some variables are easier to measure than others. When dealing with variables that are abstract or aren’t directly measurable, they will have to be operationalized, so as to turn them into measurable observations. 

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FAQs on Setting up an Experimental Design

An experimental design refers to the framework using which a research study is carried out

There are three main types of experimental design and they are: 

  1. Pre-experimental Research Design
  2. True Experimental Research Design
  3. Quasi-experimental Research Design

In experimental research, the experimental group is the group of subjects that are administered the treatment and the control group is the group of subjects that is given a placebo or no treatment at all. This allows researchers to study the effects of the treatment as any changes seen in the experimental group that isn’t seen in the control group, can directly be attributed to the treatment/independent variable. 

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