RESEARCH: Quasi Experimental Research Design

Summary

This video script from the English Simplified channel delves into quasi-experimental research design, a method aiming to establish cause and effect without random assignment. It's used when true experiments are impractical or unethical. The script outlines five types of designs, including post-test only, pre-test post-test, interrupted time series, and switching replications, each with unique procedures and data analysis methods. The goal is to provide clarity on when and how to apply these designs in real-world settings.

Takeaways

• 🧪 Quasi-experimental designs aim to establish cause and effect relationships, similar to true experiments, but without the use of random assignment.
• 🔄 Unlike true experiments, quasi-experiments do not use random sampling or random assignment, which is a method of placing participants into different treatment groups randomly.
• 🚫 Quasi-experimental designs are often used when it is unethical or impractical to conduct a true experiment, typically in field settings where random assignment is difficult.
• 👥 Quasi-experiments involve at least two groups: a control group and an experimental group, but participants are not selected through random sampling.
• 📝 There are five main types of quasi-experimental designs: post-test only non-equivalent groups, pre-test post-test non-equivalent groups, interrupted time series with non-equivalent groups, pre-test post-test with switching replication, and switching replication with treatment removal.
• 📊 Post-test only non-equivalent groups design involves a treatment given to one group and a comparison of post-tests between the experimental and control groups.
• 📉 Pre-test post-test non-equivalent groups design measures the dependent variable before and after treatment, comparing means or using statistical tests like t-test for analysis.
• 🕒 Interrupted time series design involves measurements taken at intervals over time, both before and after an intervention in non-equivalent groups.
• 🔄 Pre-test post-test with switching replication administers treatment to one group first, then switches to the control group, analyzing the dependent variable's changes.
• 🔄 Switching replication with treatment removal design involves phases where treatment is given and then removed for one group while the other group receives it later, analyzing the effects of treatment presence and absence.
• 🔑 The key difference between quasi-experimental and true experimental designs is the absence of random selection and assignment in quasi-experiments, which affects the internal validity of the research.

Q & A

What is the main difference between a quasi-experimental design and a true experiment?

The main difference is that a quasi-experimental design does not rely on random assignment of subjects to groups, unlike a true experiment which uses random sampling and assignment.

Why is quasi-experimental research used instead of a true experiment?

Quasi-experimental research is used in situations where it would be unethical or impractical to run a true experiment, often in field settings where random assignment is difficult or impossible.

What are the two groups typically involved in quasi-experimental designs?

The two groups typically involved are the control group and the experimental group.

How does the post-test only non-equivalent groups design differ from the pre-test post-test non-equivalent groups design?

In the post-test only non-equivalent groups design, there is no pre-test, and only the experimental group receives the treatment before the post-test. In contrast, the pre-test post-test non-equivalent groups design includes both a pre-test and a post-test for both groups, with the experimental group receiving the treatment in between.

What is an interrupted time series design with non-equivalent groups?

It is a variant of the pre-test post-test design where measurements are taken at intervals over time, both before and after an intervention in two or more non-equivalent groups.

How is the pre-test post-test design with switching replication applied?

In this design, a pre-test is administered to both groups, then one group receives a treatment while the other does not. After assessing the dependent variable again, the treatment is added to the control group, and the dependent variable is assessed one last time.

What is the purpose of the switching replication with treatment removal design?

This design is used to assess the effects of both the introduction and removal of a treatment by administering it to one group first, then to the other group, and analyzing the dependent variable's changes over time.

How is data analyzed in a post-test only non-equivalent groups design?

The data is analyzed by comparing the post-test results of the two groups, which includes the experimental group that received the treatment and the control group that did not.

What statistical analysis is often used in the pre-test post-test non-equivalent groups design?

The data is often analyzed using a t-test to compare the mean of the post-test results between the two groups.

How does the interrupted time series design with non-equivalent groups help in understanding the impact of an intervention?

This design helps by providing a series of measurements over time, allowing for the analysis of trends and the impact of the intervention at different points in time for both the experimental and control groups.

What is the significance of random sampling and random assignment in true experimental research?

Random sampling and assignment are crucial in true experimental research to reduce bias and ensure that the results can be generalized to the population, establishing a stronger cause-and-effect relationship.

Outlines

00:00

🔬 Introduction to Quasi-Experimental Research

This paragraph introduces the concept of quasi-experimental research design, which aims to establish a cause-and-effect relationship without the use of random assignment. It distinguishes quasi-experiments from true experiments by explaining the lack of random sampling and assignment in the former. The paragraph outlines the structure of the discussion, which includes understanding what quasi-experimental research is, its applications, how it's conducted, its types, and data analysis methods. It sets the stage for an in-depth exploration of quasi-experimental designs in various contexts where random assignment is not feasible.

05:02

📚 When to Use Quasi-Experimental Design

This section delves into the specific situations where quasi-experimental designs are most applicable, particularly when conducting a true experiment would be unethical or impractical. It highlights the use of quasi-experiments in field settings and explains the composition of the sample into control and experimental groups without the benefit of random selection. The paragraph emphasizes the ethical considerations and practical constraints that lead researchers to opt for quasi-experimental designs over true experiments.

10:06

🔍 Application and Types of Quasi-Experimental Designs

The paragraph discusses the application of quasi-experimental designs and outlines their various types. It describes five distinct types: post-test only non-equivalent groups design, pre-test post-test non-equivalent groups design, interrupted time series design with non-equivalent groups, pre-test post-test design with switching replication, and switching replication with treatment removal design. Each design is briefly explained in terms of its procedure, from pre-testing to post-testing, and the treatment administration differences between experimental and control groups. The paragraph provides a foundation for understanding how each design facilitates the comparison and analysis of data to draw meaningful conclusions.

📈 Detailed Examination of Quasi-Experimental Design Procedures

This paragraph provides a detailed examination of the procedures involved in different types of quasi-experimental designs. It explains the step-by-step process for each design, from administering pre-tests to post-tests and the timing of treatment administration. The paragraph clarifies how data is analyzed in each design, emphasizing the importance of comparing post-test results and using statistical methods like t-tests to infer causality. It offers a comprehensive look at the methodology behind quasi-experimental research, showcasing the nuances of each design and their respective data analysis techniques.

📝 Conclusion and Summary of Quasi-Experimental Research

The final paragraph summarizes the key points discussed in the video script about quasi-experimental research design. It reiterates the main difference between quasi-experiments and true experiments, which is the absence of random selection and assignment in the former. The paragraph lists the five types of quasi-experimental designs and briefly describes the unique features of each, such as the presence or absence of pre-tests, the timing of treatments, and the structure of data analysis. The summary serves to reinforce the understanding of quasi-experimental designs and sets the stage for future discussions on true experimental and factorial designs.

Keywords

💡Quasi-experimental design

Quasi-experimental design is a research approach that attempts to establish a cause-and-effect relationship between variables, similar to a true experiment, but without the use of random assignment. In the video, this concept is central as it distinguishes quasi-experiments from true experiments, which rely on random sampling and assignment. An example from the script illustrates this as subjects are assigned to groups based on non-random criteria.

💡Cause and effect

Cause and effect refers to the relationship where one event (the cause) influences another event (the effect). The video discusses how quasi-experimental designs aim to establish this relationship, particularly between an independent variable (the cause) and a dependent variable (the effect), despite not using random assignment.

💡Random assignment

Random assignment is a process used in true experiments to allocate subjects to different groups in a way that each subject has an equal chance of being selected. The script explains that quasi-experiments do not use random assignment, which is a key difference from true experiments and impacts the internal validity of the research.

💡Non-equivalent groups

Non-equivalent groups are groups of participants in a study that are not formed through random assignment and may differ from each other in systematic ways. The script mentions this term in the context of quasi-experimental designs, where groups such as experimental and control groups are compared after the experimental group receives a treatment.

💡Pre-test and post-test

Pre-test and post-test refer to measurements taken before and after an intervention or treatment in a study. The video explains that in certain quasi-experimental designs, such as the pre-test post-test non-equivalent groups design, the dependent variable is measured at two points in time to assess the impact of the treatment.

💡Interrupted time series design

Interrupted time series design is a type of quasi-experimental design that involves taking measurements at intervals over time, both before and after an intervention. The script describes this design as a variant of the pre-test post-test design, where the treatment is administered over a period, and its effects are observed over time.

💡Switching replication

Switching replication is a feature of some quasi-experimental designs where the treatment is given to one group initially and then later to a control group, allowing for multiple observations of the treatment's effects. The script outlines this concept in the context of pre-test post-test design with switching replication, where the treatment is administered to the control group after being given to the experimental group.

💡Treatment removal

Treatment removal is a concept where, after an intervention has been applied to a group, it is subsequently stopped to observe any changes or reversal of effects. The script discusses this in the context of the switching replication with treatment removal design, where the treatment is halted for the experimental group to observe the impact.

💡Ethical considerations

Ethical considerations refer to the moral principles and guidelines that researchers adhere to when conducting studies, especially regarding the treatment of participants. The video mentions that quasi-experimental designs are often used when it would be unethical or impractical to run a true experiment, indicating a respect for participant well-being over methodological purity.

💡Field settings

Field settings refer to real-world environments outside of a controlled laboratory, where research is conducted. The script notes that quasi-experiments are likely to be conducted in field settings where random assignment is challenging, reflecting the practical application of research in everyday contexts.

💡Statistical analysis

Statistical analysis involves the use of mathematical tools to interpret data and draw conclusions. In the context of the video, statistical analysis, such as t-tests, is used to compare the means of post-tests between groups in quasi-experimental designs to determine the significance of the treatment effect.

Highlights

Introduction to quasi-experimental research design, a method to establish cause and effect without random assignment.

Difference between quasi-experimental and true experiments, particularly the lack of random sampling and assignment in the former.

Quasi-experimental design's resemblance to true experiments but with non-random criteria for group assignment.

Ethical and practical limitations that make quasi-experimental design preferable over true experiments.

Quasi-experiments are often conducted in field settings where random assignment is not feasible.

Existence of two main groups in quasi-experimental designs: control and experimental.

Explanation of the five types of quasi-experimental designs and their unique applications.

Description of the post-test only non-equivalent groups design and its procedure.

The pre-test post-test non-equivalent groups design, including its steps and data analysis method.

Interrupted time series design with non-equivalent groups, focusing on measurements over time.

Pre-test post-test design with switching replication and its iterative treatment application process.

Switching replication with treatment removal design, detailing the phases and analysis of data.

Summary of the key features of the post-test only non-equivalent groups design.

Summary of the pre-test post-test design with non-equivalent groups, emphasizing statistical analysis.

Summary of the interrupted time series design, highlighting the importance of time-based measurements.

Overview of the pre-test post-test design with switching replication, focusing on treatment administration and analysis.

Final summary of the quasi-experimental research design, its types, and their respective procedures and analyses.

Announcement of upcoming topics on true experimental research design and factorial design.

Transcripts

hi there how are you doing welcome back to english simplified channel as we had already  

discussed what experimental research is and one of its type that is pre-experimental so in this  

session we are discussing its second type that is quasi-experimental research design  

in order to understand this easily so i divide the discussion into a what is quasi-experimental  

b when is it used c how is it applied d what are its types and how its data is analyzed  

well are you ready let's get started

part a what is quasi-experimental like a  true experiment a quasi-experimental design  

aims to establish a cause and effect relationship between an independent and dependent variable  

however unlike a true experiment a  quasi-experiment does not rely on random  

assignment instead subjects are assigned  to groups based on non-random criteria  

so in conclusion this quasi-experimental research  is research that resembles experimental research  

but is not true experimental research because it doesn't use random assignment in which it is a way  

of placing participants from your sample into different treatment groups using randomization

as you have to know a true experimental should apply random sampling and random assignment  

in selecting the sample random sampling also called probability sampling or random selection  

is a way of selecting members of a population to be included in your study while you use random  

assignment to place participants or sample into  the control or experimental group in fact in  

quasi-experimental these procedures aren't applied that's why it's named as quasi-experimental design

well now let's continue to part  b when is quasi-experimental used  

quasi-experimental design is most useful in situations where it would be unethical or  

impractical to run a true experiment in other words quasi experiments are most likely to be  

conducted in field settings in which random assignment is difficult or impossible bear in  

mind quasi-experimental has two groups of sample  namely control and experimental groups but this  

sample on selected by random sampling and random  assignment as i have already mentioned it before

all right and this is part see how is  quasi-experimental applied as there are  

some types of quasi-experimental and the way  they are applied is different for each type  

then to answer this question we  have to discuss it type by type  

and continue to the next part that is party  what are its types and how a stator is analyzed  

well the types of quasi-experimental are such as  one post-test only non-equivalent groups design  

two pre-test post-test non-equivalent groups  design three interrupted time series design  

with non-equivalent groups four pre-test  post test design with switching replication  

and five switching replication with treatment  removal design all right let's see one by one

number one post-test only  non-equivalent groups design  

in this design participants in one group are  exposed to treatment a non-equivalent or control  

group is not exposed to the treatment and then  the two groups are compared what does this mean  

let's see the procedure post test only  non-equivalent groups design has two groups  

of sample they are experimental and control groups  treatment is only given to the experimental group  

or the control group is with no treatment  after that the two groups are tested which is  

called post test so it means there is only post  test in this design or this design is without  

pre-test then finally the data is analyzed  by comparing the post-test of the two groups

now let's see and discuss the second type  of quasi-experimental that is 2. pre-test  

post-test non-equivalent groups design in  a pre-test post-test design the dependent  

variable is measured once before the treatment is  implemented and once after it is implemented let's  

see its procedure this design also has two groups  of sample they are control and experimental groups  

the first step is to address pre-test to the  two groups then it is continued by giving the  

treatment to only experimental group having  finished giving the treatment then the two  

groups are tested once again with what it's  called post test and to make the conclusion  

then the data is analyzed by comparing the  mean of the post-test of the two groups or  

by statistical analysis of t-test okay now we're  discussing the third type of quasi-experimental  

that is three interrupted time series design with  non-equivalent groups a variant of the pre-test  

post test design is the interrupted time series  design a time series is a set of measurements  

taken at intervals over a period of time in  addition the interrupted time series designed  

with non-equivalent groups involves taking a set  of measurements at intervals over a period of time  

both before and after an intervention of  interest in two or more non-equivalent groups  

let's see how it is done or applied the first  step is to give pre-test to the two groups  

then treatment is given here you have to know  the treatment given is by some periods of time  

as in this example treatment is given each  week for six months to the experimental group  

while the control group doesn't  receive the treatment after that  

the two groups are post-tested and finally  the data is analyzed to draw the conclusion

well the next type of quasi-experimental  is pre-test post-test design with switching  

replication in pre-test post-test  design with switching replication  

is done by using a pre-test post-test  design with switching replication design  

non-equivalent groups are administered  a pre-test of the dependent variable  

then one group receives a treatment while a  non-equivalent control group does not receive a  

treatment the dependent variable is assessed again  and then the treatment is added to the control  

group and finally the dependent variable is  assessed one last time okay let's see it procedure  

the first step is by addressing pretest to the  two groups then treatment is firstly given to  

the experimental group while for the control  group is held off after that the two groups  

are post-tested then the treatment is given to the  control group after giving it the control group is  

again post-tested and finally the conclusion  is made by comparing and analyzing the data

and now we have come to last  type of quasi-experimental  

that is switching replication  with treatment removal design  

in a basic pre-test post-test design with  switching replication the first group receives  

a treatment and the second group receives  the same treatment a little bit later on  

while the initial group continues to receive  the treatment all right let's see its procedure

this design at least has two phases for example a  research is conducted in two phases in two weeks  

so in phase one and week one both the  experimental and control groups are  

pre-tested then the treatment is firstly given  to the experimental group while for the control  

group is held off after that the two groups  are tested again with a test namely post-test  

then finally the data is analyzed and saved

next in phase 2 week 2 the treatment is stopped  for experimental group while the control group  

is now receiving the treatment after the  treatment is done for the control group  

again the two groups are post-tested and finally  the data is analyzed to draw the conclusion

all right now let's make the conclusion  and summary one a quasi-experiment is a  

type of research design that attempts to  establish a cause and effect relationship  

the main difference with a true experiment is that  the groups are not randomly selected and assigned  

two there are five types of quasi-experiment  designs that are between subjects and nature they  

are one the post-test only non-equivalent groups  design two the pre-test post-test design with  

non-equivalent groups three the interrupted  time series design with non-equivalent groups  

four the pre-test post test design with switching  replication and five the switching replication  

with treatment removal design in post-test only  non-equivalent groups design has two groups of  

sample they are experimental and control groups  treatment is only given to the experimental group  

or the control group is with no treatment after  that the two groups are tested which is called  

post test so it means there is only post test in  this design or this design is without pre-test

two the pre-test post test design with  non-equivalent groups this design also  

has two groups of sample they are control and  experimental groups the first step is to address  

pre-test to the two groups then it is continued  by giving the treatment to only experimental group  

having finished giving the treatment then  the two groups are tested once again with  

what it's called post-test and to make  the conclusion then the data is analyzed  

by comparing the mean of the post-test of the  two groups or by statistical analysis of t-test

three the interrupted time series design with  non-equivalent groups the first step is to give  

pre-test to the two groups then treatment is  given here you have to know the treatment given  

is by some periods of time as in this example  treatment is given each week for six months  

to the experimental group while the control  group doesn't receive the treatment after that  

the two groups are post-tested and finally  the data is analyzed to draw the conclusion

for the pre-test post-test design with switching  replication the first step is by addressing  

pre-test to the two groups then treatment  is firstly given to the experimental group  

while for the control group is held off after  that the two groups are post-tested then the  

treatment is given to the control group after  giving it the control group is again post-tested  

then finally the conclusion is made  by comparing and analyzing the data

and the last type is number five the switching  replication with treatment removal design  

this design at least has two phases for example a  research is conducted in two phases in two weeks  

so in phase one and week one both the  experimental and control groups are pre-tested  

then the treatment is firstly given to the  experimental group while for the control  

group is held off after that the two groups  are tested again with a test namely post test  

then finally the data is analyzed and saved

next in phase 2 week 2 the treatment is stopped  for experimental group while the control group  

is now receiving the treatment after the  treatment is done for the control group  

again the two groups are post-tested and finally  the data is analyzed to draw the conclusion

well that's at our discussion relating  to quasi-experimental research design  

hopefully this explanation has broadened  your knowledge as we have already covered  

pre-experimental research design and  quasi-experimental research design  

then our next topic of discussion will be true  experimental research design and factorial  

design by the way don't forget to support my  channel by your subscribe thanks and tartare