Quantitative research designs experimental quasi experimental and descriptive

INTRODUCTION

Overview of Quantitative Designs

There are three major types of quantitative research designs: experimental, quasi-experimental, and non- experimental. Non-experimental research includes descriptive, correlational, and survey research. In this unit, we will discuss experimental and quasi-experimental research designs, and in Unit 5 we will cover non- experimental quantitative research designs.

Researchers want to protect their research against any threats to validity and reliability. Research design is one way they do this (Trochim, 2006). In general, you want to use as many approaches as you can to reduce or eliminate threats to validity. Other ways include logical arguments, measuring the threat itself to show it does not invalidate the study, using statistics to gauge the impact of other variables, and so on.

According to Trochim's (2006) Research Methods Knowledge Base Web site, settling on your design begins with two simple questions:

• Question 1: Is random assignment used? If you answer yes to the first question, your design will be a randomized or true experimental design. If you answer no to the first question, you must ask the second question.

• Question 2: Is there a control group or multiple measures? Answering yes to this question means that your design will be a quasi-experimental design. Answering no means that you have a non-experimental design.

Experimental Research

Experimental studies compare the effect of one or more independent variables on one or more dependent variables. The independent variable, or presumed cause, is manipulated by the researcher. In this case, when a variable is manipulated or controlled by the researcher, this means the research can control whether research participants are exposed to that variable. The hallmark of experimental designs is the random assignment of participants to the levels of the independent variable. Causation can be inferred in true experimental research. Leedy and Ormrod (2013) provide a thorough description of the different types of experimental designs (p. 234 –237). These are the ones numbered Designs 4–7. Certain types of single-subject experiments can also be classified as experimental designs. As such, causal attributions can be inferred (Meltzoff, 1998).

Research questions that require an experimental approach ask questions about the causal effect of one variable on another. For example, a researcher might ask, "Does tutoring affect test scores?" Because this question asks whether tutoring (the independent variable) affects test scores (the dependent variable), it is asking about a causal relationship. This can only be answered with confidence using an experimental approach, which would require the researcher to be able to manipulate tutoring. In other words, the researcher must to be able to randomly assign research participants to receive tutoring or not receive it, and compare the test scores of the two groups. If there is a statistically significant difference, the researcher is in a position to be able to conclude that tutoring caused the difference in the test scores.

Approaches

Unit 4 Quantitative Methods: Experimental and Quasi-Experimental

Quasi-Experimental Research

Quasi-experimental research designs come in many different forms. Like experimental research, the researcher aims to compare the effect of one or more independent variables on one or more dependent variables. However, the researcher does not or cannot randomly assign participants to the comparison groups, due to ethical or logistical concerns, so cause-and-effect relationships cannot be conclusively established.

Research questions that require a quasi-experimental approach ask about group differences or differences in conditions. For example, a research might ask, "Is there a difference in test scores of students enrolled in different sections of the same class?" A researcher would not have assigned the students to be in one class section or another. The students either would have signed up for a course section, or been assigned to a section by an advisor, guidance counselor, or registrar. Since the researcher cannot randomly assign the research participants to the class sections, a quasi-experimental approach is needed. Another example of a research question that would require a quasi-experimental approach might be "Do the test scores of students improve after they receive tutoring?" This question requires a comparison of at least two scores in one group of participants, basically a pretest and a post test. The researcher would have to collect test scores from the participants before the tutoring and after the tutoring, and compare the scores. The researcher would not be able to conclude a definitive causal relationship between the variables in either example.

It is particularly important that the researcher carefully considers the threats to validity in the interpretation of the results of quasi-experimental research designs. Leedy and Ormrod (2013) describe various types of quasi- experimental research in their text (p. 237–241). These are the designs numbered 8–13.

References

Leedy, P. D., & Ormrod, J. E. (2013). Practical research: Planning and design (10th ed.). Upper Saddle River, NJ: Pearson.

Meltzoff, J. (1998). Critical thinking about research: Psychology and related fields. Washington, DC: American Psychological Association.

Trochim, W. M. K. (2006). Research methods knowledge base. Retrieved from http://www.socialresearchmethods.net/kb/index.php

OBJECTIVES

To successfully complete this learning unit, you will be expected to:

1. Distinguish between experimental and quasi-experimental design.

2. Describe treatment conditions in a scientific study.

[u04s1] Unit 4 Study 1

STUDIES

Readings

Read the introduction to this unit, Quantitative Methods: Experimental and Quasi-Experimental Approaches. This reading will introduce you to the defining characteristics of experimental and quasi-experimental approaches.

Note: This course, as well as other courses and other academic sources, uses the term approach to specifically refer to the major types of either methodology (qualitative methodology or quantitative methodology). For example, you have learned that there are three quantitative approaches: experimental, quasi-experimental, and non-experimental. Variations within each approach are called designs , such as simple time-series design . Some sources, such as Trochim's Research Methods Knowledge Base Web site, use the term design in a broader way than this course does, using it to refer to an approach as well. In this course, approach will refer to the major types of each methodology, and design will be subtypes of the approaches.

Use your Leedy and Ormrod text to complete the following:

• Read Chapter 7, "Experimental, Quasi-Experimental, and Ex Post Facto Designs," pages 178–210. This chapter discusses the differences in experimental and quasi-experimental approaches, as well as specific designs for each approach. The chapter includes diagrams and examples to illustrate the various designs.

• Use Trochim's Research Methods Knowledge Base Web site to read the following pages. These present additional information to aid your understanding of the experimental and quasi-experimental approaches.

◦ Introduction to Design. ◦ Types of Designs. ◦ Experimental Design. ◦ Quasi-Experimental Design.

Library Search

• Use the Library to locate an article from the academic literature that utilizes either an experimental or quasi-experimental approach. The Finding Articles by Type: Experimental Research and Finding Articles by Type: Quasi-Experimental Research guides will show you some techniques for searching for experimental and quasi-experimental articles in the library databases.

• Record the persistent link for each article found within the library databases. The persistent link is different from the URL in the browser window. Use this guide to learn where to locate your articles' persistent links: Persistent Links and DOIs.

• Read the article in preparation for this unit's discussions. • Use Finding Articles for Your Discussion Post to learn how to locate articles within the library

databases. This guide will walk you through the basic steps of accessing the library databases and creating a search strategy to find articles.

Optional Program-Specific Content

Some programs have opted to provide program-specific content designed to help you better understand how the subject matter in this study is incorporated into your particular field of study. Check below to see if your program has any suggested readings for you.

SOBT Learners

• Eisenhardt, K. M., & Graebner, M. E. (2007). "Theory building from cases: Opportunities and challenges." Academy of Management Journal, 50(1), 25–32. This reading is a companion to the Eisenhardt 1989 paper and provides additional guidance on the case study approach described in that paper.

[u04a1] Unit 4 Assignment 1 

RESEARCH TOPIC AND METHODOLOGY DESCRIPTION

Resources

Research Topic and Methodology Description Scoring Guide.

APA Style and Format.

Research Topic and Methodology Form.

In this assignment, you will complete the Research Topic and Methodology Form linked in the Resources. You must use the research study that you selected in the Unit 2 assignment, and your instructor must have approved the study.

Fill out all sections of the form with the information requested. You are expected to use professional, academic writing skills and proper APA citations and references. You should state information in your own words. However, if you find it necessary to use material verbatim from another source, it must be quoted with an appropriate citation for quotes.

Refer to the project description and the assignment scoring guide to make sure you meet the requirements of this assignment.

Submit your completed form in the assignment area.

[u04d1] Unit 4 Discussion 1 

QUANTITATIVE RESEARCH: EXPERIMENTAL RESEARCH

Using the experimental or quasi-experimental study you selected in this unit's studies, in the Library Search section, complete the following:

• Determine whether the study is experimental or quasi-experimental; describe how you know. • Describe the variables, both independent and dependent, used in the research. • Describe the treatment conditions of the experimental group. If quasi-experimental, describe the

different groups or conditions that were compared. • Describe the specific type of research design that was used and discuss why it is considered

experimental or quasi-experimental. • Evaluate the scientific merit of the selected design. How might you have designed this study

differently? Evaluate how well the experimental approach and design helped the researcher answer the research questions.

• List the persistent link for the article in your response. Refer to the Persistent Links and DOIs guide, linked in Resources, to learn how to locate this information in the library databases.

• Cite all sources in APA style and provide an APA-formatted reference list at the end of your post.