Quantitative, Qualitative, and Mixed Research
This chapter is our introduction to the three research methodology paradigms. A paradigm is a perspective based on a set of assumptions, concepts, and values that are held by a community or researchers. For the most of the 20th century the quantitative paradigm was dominant. During the 1980s, the qualitative paradigm came of age as an alternative to the quantitative paradigm, and it was often conceptualized as the polar opposite of quantitative research. Finally, although the modern roots of mixed research go back to the late 1950s, I think that it truly became the legitimate third paradigm with the publication of the Handbook of Mixed Methods in Social and Behavioral Research (2003, by Tashakkori and Teddlie). At the same time, mixed research has been conducted by practicing researchers throughout the history of research.
Characteristics of the Three Research Paradigms
There are currently three major research paradigms in education (and in the social and behavioral sciences). They are quantitative research, qualitative research, and mixed research. Here are the definitions of each:
Here is Table 2.1 for your convenience and review.
Quantitative Research Methods:
Experimental and Nonexperimental Research
The basic building blocks of quantitative research are variables.
Variables (something that takes on different values or categories) are
the opposite of constants (something that cannot vary, such as a single
value or category of a variable).
Many of the important types of variables used in quantitative research are shown, with examples, in Table 2.2.
Here is that table for your review:
In looking at the table note that when we speak of measurement, the most simple classification is between categorical and quantitative variables. As you can see, quantitative variables vary in degree or amount (e.g., annual income) and categorical variables vary in type or kind (e.g., gender).
The other set of variables in the table (under the heading role taken by the variable) are the kinds of variables we talk about when explaining how the world operates and when we design a quantitative research study.
As you can see, independent variables (symbolized by "IV") are the presumed cause of another variable. Dependent variables (symbolized by "DV") are the presumed effect or outcome. Dependent variables are influenced by one or more independent variables. What is the IV and DV in the relationship between smoking and lung cancer? (Smoking is the IV and lung cancer is the DV.)
Sometimes we want to understand the process or variables through which one variable affects another variable. This brings us to the idea of intervening variables (also called mediator or mediating variables). Intervening variables are variables that occur between two other variables. For example, tissue damage is an intervening variable in the smoking and lung cancer relationship. We can use arrows (which mean causes or affects) and draw the relationship that includes an intervening variable like this:
Smoking---->Tissue Damage---->Lung Cancer.
Sometimes a relationship does not generalize to everyone; therefore, researchers often use moderator variables to show how the relationship changes across the levels of an additional variable. For example, perhaps behavioral therapy works better for males and cognitive therapy works better for females. In this case, gender is the moderator variable. The relationship be type of therapy (behavioral versus cognitive) and psychological relief is moderated by gender.
Now, I will talk about the major types of quantitative research: experimental and nonexperimental research.
The purpose of experimental research is to study cause and effect relationships.
Its defining characteristic is active manipulation of an
independent variable (i.e., it is only in experimental research that
“manipulation” is present). Also, random assignment (which creates
"equivalent" groups) is used in the strongest experimental research
Here is an example of an experiment.
Pretest Treatment Posttest
O1 XC O2
· E stands for the experimental group (e.g., new teaching approach)
· C stands for the control or comparison group (e.g., the old or standard teaching approach)
Because the best way to make the two groups similar in the above research design is to randomly assign the participants to the experimental and control groups, let’s assume that we have a convenience sample of 50 people and that we randomly assign them to the two groups in our experiment.
Here is the logic of this experiment. First, we made our groups approximately the same at the start of the study by using random assignment (i.e., the groups are “equated”). You pretest the participants to see how much they know. Next, you manipulate the independent variable by using the new teaching approach with the experimental group and using the old teaching approach for the control group. Now (after the manipulation) you measure the participants’ knowledge to see how much they know after having participated in our experiment. Let’s say that the people in the experimental group show more knowledge improvement than those in the control group. What would you conclude? In this case, we can conclude that there is a causal relationship between the IV, teaching method, and the DV, knowledge, and specifically we can conclude that the new teaching approach is better than the old teaching approach. Make sense?
Now, let’s say that in the above experiment we could not use random assignment to equate our groups. Let’s say that, instead, we had our best teacher (Mrs. Smith) use the new teaching approach with her students in her 5th period class and we had a newer and less experienced teacher (Mr. Turner) use the old teaching approach with his 5th period class. Let’s again say that the experimental group did better than the control group. Do you see any problems with claiming that the reason for the difference between the two groups is because of the teaching method? The problem is that there are alternative explanations. First, perhaps the difference is because Mrs. Smith is the better teacher. Second, perhaps Mrs. Smith had the smarter students (remember the students were not randomly assignment to the two groups; instead, we used two intact classrooms). We have a name for the problems just mentioned. It is the problem of alternative explanations. In particular, it is very possible that the difference we saw between the two groups was due to variables other than the IV. In particular, the difference might have been due to the teacher (Mrs. Smith vs Mr. Turner) or to the IQ levels of the groups (perhaps Mrs. Smith’s students had higher IQs than Mr. Smith’s students) We have a special name for these kinds of variables. They are called extraneous variable.
It is important to remember the definition of an extraneous variable because they can destroy the integrity of a research study that claims to show a cause and effect relationship. An extraneous variable is a variable that may compete with the independent variable in explaining the outcome. Remember this, if you are ever interested in identifying cause and effect relationships you must always determine whether there are any extraneous variables you need to worry about. If an extraneous variable really is the reason for an outcome (rather than the IV) then we sometimes like to call it a confounding variable because it has confused or confounded the relationship we are interested in.
Remember that the defining characteristic of experimental research was manipulation of the IV. Well, in nonexperimental research there is no manipulation of the independent variable. There also is no random assignment of participants to groups.
What this means is that if you ever see a relationship between two variables in nonexperimental research you cannot jump to a conclusion of cause and effect because there will be too many other alternative explanations for the relationship.
In the chapter, we make a distinction between two examples of nonexperimental research. In the "basic case" of causal-comparative research, there is one categorical IV and one quantitative DV.
· Example: Gender (IV) and class performance (DV).
· You would look for the relationship by comparing the male and female average performance levels.
In the simple case of correlational research, there is one quantitative IV and one quantitative DV.
· Example: Self-esteem (IV) and class performance (DV).
· You would look for the relationship by calculating the correlation coefficient.
· The correlation coefficient is a number that varies between –1 and +1, and 0 stands for no relationship. The farther the number is from 0, the stronger the relationship.
· If the sign of the correlation coefficient is positive (e.g., +.65) then you have a positive correlation, which means the two variables move in the same direction (as one variable increases, so does the other variable). Education level and annual income are positively correlated (i.e., the higher the education, the higher the annual income).
· If the sign of the correlation coefficient is negative (e.g., -.71) then you have a negative correlation, which means the two variables move in opposite directions (as one variable increases, the other decreases). Smoking and life expectancy are negatively correlated (i.e., the higher the smoking, the lower the life expectancy).
We will show you how to improve on the two basic nonexperimental designs in later chapters, but for now, please remember these important points:
1) You can obtain much stronger evidence for causality from experimental research than from nonexperimental research (e.g., a strong experiment is better than causal-comparative and correlation research).
2) You cannot conclude that a relationship is causal when you only have one IV and one DV in nonexperimental research (without controls). Therefore, the basic cases of both causal-comparative and correlation research are severely flawed!
3) In later chapters we explain three necessary conditions for causality (relationship, temporal order, and lack of alternative explanations)
For a preview of these three necessary conditions required to make a firm statement of cause and effect, read this next section. It is provided as supplemental or preview material for this topic which occurs in many chapters of the book. If you have had enough for now, just skip to the next section of this lecture entitled Qualitative Research.
There are three necessary conditions that you must establish whenever you want to conclude that a relationship is causal. They are shown in the following Table:
Our experiment met these criteria quite nicely. That is, we had a relationship between teaching method and knowledge; the manipulation occurred before the posttest; and because we randomly assigned the people to the two groups, there should be no other variables that can explain away the relationship.
On the other hand, in the basic cases of causal-comparative and correlational research, where we only observed a relationship between two variables (we had no manipulation or random assignment), we have only established condition 1. We can only conclude that the two variables are related. In chapter 11 we will show you how to design nonexperimental research that performs better than the basic cases on the three above conditions.
Still, remember, even when these basic cases are improved, experimental research with random assignment is better for studying cause and effect than nonexperimental research. Another way of saying this is, if you want to show that one thing causes another thing, then, if it is feasible, you will want to CONDUCT AN EXPERIMENT.
Qualitative Research Methods
We describe qualitative research earlier, in Table 2.1. There are five major types of qualitative research: phenomenology, ethnography, case study research, grounded theory, and historical research. All of the approaches are similar in that they are qualitative approaches. Each approach, however, has some distinct characteristics and tends to have its own roots and following.
Here are the definitions and an example of the different types of qualitative research:
· Phenomenology – a form of qualitative research in which the researcher attempts to understand how one or more individuals experience a phenomenon. For example, you might interview 20 widows and ask them to describe their experiences of the deaths of their husbands.
· Ethnography – is the form of qualitative research that focuses on describing the culture of a group of people. Note that a culture is the shared attitudes, values, norms, practices, language, and material things of a group of people. For an example of an ethnography, you might decide to go and live in a Mohawk communities and study the culture and their educational practices.
· Case study research – is a form of qualitative research that is focused on providing a detailed account of one or more cases. For an example, you might study a classroom that was given a new curriculum for technology use.
· Grounded theory – is a qualitative approach to generating and developing a theory form data that the researcher collects. For an example, you might collect data from parents who have pulled their children out of public schools and develop a theory to explain how and why this phenomenon occurs, ultimately developing a theory of school pull-out.
· Historical research – research about events that occurred in the past. An example, you might study the use of corporeal punishment in schools in the 19th century.
Mixed Research Methods
Mixed research is a general type of research (it’s one of the three paradigms) in which quantitative and qualitative methods, techniques, or other paradigm characteristics are mixed in one overall study. Earlier we showed it major characteristics of mixed research in Table 2.1. Now the two major types of mixed research are distinguished: mixed method versus mixed model research.
The Advantages of Mixed Research
First of all, we advocate the use of mixed research when it is feasible. We are excited about this new movement in educational research and believe it will help qualitative and quantitative researchers to get along better and, more importantly, it will promote the conduct of excellent educational research.
Our Research Typology
We have now covered the essentials of the three research paradigms and their subtypes. Let’s put it all together in the following picture of our research typology: