What type of research has the primary advantage of allowing a scientist to determine cause and effect relationships?

There are five basic types of research studies, each designed to answer different kinds of questions. The five types of studies are discussed below. 

1. Case Studies

Case studies look at a single subject (e.g., a child with autism) or a single case (e.g., a classroom for children with autism). Case studies are typically used in research that describes the development of an individual, group, or situation over a period of time in order to provide a detailed account of what is occurring within its real-life context.

• The advantage of a case study is that it allows the researcher to gather a lot of information about one person or one case.
• The disadvantage of a case study is that the information gathered about one person or a small group of people cannot readily be applied or generalized to other people or other cases in other situations or other settings and, therefore, may be of limited use.

Click here to check out a sample case study. 

2. Correlational Studies

Correlational studies look for a relationship between two or more variables, or things, that naturally occur in the same environment. Correlational studies cannot tell us anything about cause and effect, only that there is a relationship between two or more things. For example, a study might be designed to determine if there is a relationship between the number of children with autism in a particular community and the month of their birth.

Figure 1 presents a bar graph of a study of number of children with autism and month of birth. The graph illustrates that more children with autism were born in the winter months (November, December, and January) than in the summer, spring, or fall.

Although this graph shows a relationship between cases of autism in one community and month of birth, we cannot make the assumption that a winter birthday causes autism. Perhaps some other variable that we have not considered (such as an illness) is having an effect on the two variables under study.

• The advantage of correlational studies is that a lot of information about a large number of people can be gathered at one point in time.
• The disadvantage of correlational studies is that it is not possible to control other factors outside of the study that might influence the research.

Click here to check out a sample correlational study.

3. Longitudinal Studies

Longitudinal studies can give us information about how people develop over time. These types of studies follow one group of people (referred to as a cohort) across time, measuring the same behavior multiple times. For example, we may want to determine if children with autism do better on performance tests in self-contained than in inclusive classrooms. The best research design for answering this question would be to follow one cohort of children with autism that spent time in both environments.

In Figure 2, this design is presented with a line graph.

As illustrated in the graph, children in this cohort performed better in grades 1 and 4 when they were in inclusive classrooms than in grades 2 and 3 when they were in self-contained environments.

• The advantage of longitudinal studies is that they allow researchers to pinpoint times during development when changes occur.
• The disadvantage of longitudinal studies is that it takes a long time to complete them. (Note that in the example in Figure 2, the study took four years to complete.)

Click here to check out a sample longitudinal study.

4. Experimental Studies

Experimental studies are controlled so that the researcher manipulates one variable to determine its effect on other variables. Two primary types of experimental studies are used in intervention development and testing: randomized group design and single-case design.

The first type includes experimental group designs in which participants are randomly assigned either to receive the intervention (the experimental group) or to a control group. The control group completes all the same steps as the experimental group, except they do not receive the intervention that is under investigation. Therefore, if the study is well controlled, it can be concluded that the differences between the experimental and control groups at the end of the study are due to the intervention.

A second type of experimental study frequently used in intervention research is single-case design (SCD). Many studies involving children with autism, particularly those examining behavioral and educational treatments, use single-case designs. Rather than examining differences across participant groups that do and do not receive an intervention, single-case designs involve individual participants or a small cluster of participants who provide their own control for comparison. For example, a researcher may be interested in determining whether a new communication intervention tool on tablet devices improves communication skills.

• The advantage of randomized experimental studies is that the research design allows researchers to examine cause-and-effect relationships.
• The disadvantage of a randomized experimental study is that the results cannot always be generalized to the real world. This is because this kind of study lacks “real-world” authenticity; that is, what occurs in a controlled environment of a study may be very different from what might occur in a real-life setting, such as a typical classroom.

Click here to check out a sample experimental study. 

5. Clinical Trial Studies

Clinical trial studies are one specific type of randomized group experimental study. Clinical trial studies are most likely to be conducted in medical or other clinical settings. Similar to experimental group design studies, clinical trial studies employ an experimental/control group, in which participants are randomly assigned to receive the experimental treatment (e.g., a medication to treat autism symptoms) or a placebo (a sugar pill).

In both randomized experimental group and clinical trial studies, participants are not informed about their group assignment to guard against participant expectations about intervention or treatment. In addition, in well-designed studies, experimenters are not informed about group assignment either to guard against researcher expectations about intervention or treatment. That is, if participants expect to get better because they know they are receiving treatment, they may actually get better; similarly, if researchers expect an intervention to be successful, they may perceive it as so, regardless of whether or not the treatment is actually effective! This uninformed state is what researchers refer to as being blind to the conditions of the experiment. When both participants and experimenters are uninformed, it is referred to as a double-blind study, and is a means of ensuring objective results.

• The advantage of clinical trial studies is that they can determine the effectiveness of an intervention. This is because the intervention is compared with a placebo or control condition.
• The disadvantage of clinical trial studies is the same as for randomized experimental studies; that is, the results of the study cannot always be generalized to a real-life setting.

Click here to check out a sample clinical trials study.

Reading and interpreting research can be a difficult task. However, with perseverance and practice, you can learn to comfortably navigate scientific writing for the purposes of making informed treatment decisions for your child. This section is written to give you a basic understanding of the scientific model underlying research studies. Check out OAR’s A Parent’s Guide for Research for more information.

How do researchers investigate psychological phenomena? They utilize a process known as the scientific method to study different aspects of how people think and behave.

When conducting research, the scientific method steps to follow are:

1. Observe what you want to investigate
2. Ask a research question and make predictions
3. Test the hypothesis and collect data
4. Examine the results and draw conclusions
5. Report and share the results 

This process not only allows scientists to investigate and understand different psychological phenomena but also provides researchers and others a way to share and discuss the results of their studies.

What is the scientific method and how is it used in psychology?

The scientific method consists of five steps. It is essentially a step-by-step process that researchers can follow to determine if there is some type of relationship between two or more variables.

By knowing the steps of the scientific method, you can better understand the process researchers go through to arrive at conclusions about human behavior.

While research studies can vary, these are the basic steps that psychologists and scientists use when investigating human behavior.

The following are the scientific method steps in order:

Before a researcher can begin, they must choose a topic to study. Once an area of interest has been chosen, the researchers must then conduct a thorough review of the existing literature on the subject. This review will provide valuable information about what has already been learned about the topic and what questions remain to be answered.

A literature review might involve looking at a considerable amount of written material from both books and academic journals dating back decades.

The relevant information collected by the researcher will be presented in the introduction section of the final published study results. This background material will also help the researcher with the first major step in conducting a psychology study: formulating a hypothesis.

Once a researcher has observed something and gained some background information on the topic, the next step is to ask a question. The researcher will form a hypothesis, which is an educated guess about the relationship between two or more variables

For example, a researcher might ask a question about the relationship between sleep and academic performance: Do students who get more sleep perform better on tests at school?

In order to formulate a good hypothesis, it is important to think about different questions you might have about a particular topic.

You should also consider how you could investigate the causes. Falsifiability is an important part of any valid hypothesis. In other words, if a hypothesis was false, there needs to be a way for scientists to demonstrate that it is false.

Once you have a solid hypothesis, the next step of the scientific method is to put this hunch to the test by collecting data. The exact methods used to investigate a hypothesis depend on exactly what is being studied. There are two basic forms of research that a psychologist might utilize: descriptive research or experimental research.

Descriptive research is typically used when it would be difficult or even impossible to manipulate the variables in question. Examples of descriptive research include case studies, naturalistic observation, and correlation studies. Phone surveys that are often used by marketers are one example of descriptive research.

Correlational studies are quite common in psychology research. While they do not allow researchers to determine cause-and-effect, they do make it possible to spot relationships between different variables and to measure the strength of those relationships. 

Experimental research is used to explore cause-and-effect relationships between two or more variables. This type of research involves systematically manipulating an independent variable and then measuring the effect that it has on a defined dependent variable.

One of the major advantages of this method is that it allows researchers to actually determine if changes in one variable actually cause changes in another.

While psychology experiments are often quite complex, a simple experiment is fairly basic but does allow researchers to determine cause-and-effect relationships between variables. Most simple experiments use a control group (those who do not receive the treatment) and an experimental group (those who do receive the treatment).

Once a researcher has designed the study and collected the data, it is time to examine this information and draw conclusions about what has been found. Using statistics, researchers can summarize the data, analyze the results, and draw conclusions based on this evidence.

So how does a researcher decide what the results of a study mean? Not only can statistical analysis support (or refute) the researcher’s hypothesis; it can also be used to determine if the findings are statistically significant.

When results are said to be statistically significant, it means that it is unlikely that these results are due to chance.

Based on these observations, researchers must then determine what the results mean. In some cases, an experiment will support a hypothesis, but in other cases, it will fail to support the hypothesis.

So what happens if the results of a psychology experiment do not support the researcher's hypothesis? Does this mean that the study was worthless?

Just because the findings fail to support the hypothesis does not mean that the research is not useful or informative. In fact, such research plays an important role in helping scientists develop new questions and hypotheses to explore in the future.

After conclusions have been drawn, the next step is to share the results with the rest of the scientific community. This is an important part of the process because it contributes to the overall knowledge base and can help other scientists find new research avenues to explore.

The final step in a psychology study is to report the findings. This is often done by writing up a description of the study and publishing the article in an academic or professional journal. The results of psychological studies can be seen in peer-reviewed journals such as Psychological Bulletin, the Journal of Social Psychology, Developmental Psychology, and many others.

The structure of a journal article follows a specified format that has been outlined by the American Psychological Association (APA). In these articles, researchers:

• Provide a brief history and background on previous research
• Present their hypothesis
• Identify who participated in the study and how they were selected
• Provide operational definitions for each variable
• Describe the measures and procedures that were used to collect data
• Explain how the information collected was analyzed
• Discuss what the results mean

Why is such a detailed record of a psychological study so important? By clearly explaining the steps and procedures used throughout the study, other researchers can then replicate the results. The editorial process employed by academic and professional journals ensures that each article that is submitted undergoes a thorough peer review, which helps ensure that the study is scientifically sound.

Once published, the study becomes another piece of the existing puzzle of our knowledge base on that topic.

Before you begin exploring the scientific method steps, here's a review of some key terms and definitions that you should be familiar with:

• Falsifiable: The variables can be measured so that if a hypothesis is false, it can be proven false
• Hypothesis: An educated guess about the possible relationship between two or more variables
• Variable: A factor or element that can change in observable and measurable ways
• Operational definition: A full description of exactly how variables are defined, how they will be manipulated, and how they will be measured
  

The goals of psychological studies are to describe, explain, predict and perhaps influence mental processes or behaviors. In order to do this, psychologists utilize the scientific method to conduct psychological research. The scientific method is a set of principles and procedures that are used by researchers to develop questions, collect data, and reach conclusions.

Researchers seek not only to describe behaviors and explain why these behaviors occur; they also strive to create research that can be used to predict and even change human behavior.

Psychologists and other social scientists regularly propose explanations for human behavior. On a more informal level, people make judgments about the intentions, motivations, and actions of others on a daily basis.

While the everyday judgments we make about human behavior are subjective and anecdotal, researchers use the scientific method to study psychology in an objective and systematic way. The results of these studies are often reported in popular media, which leads many to wonder just how or why researchers arrived at the conclusions they did.

Now that you're familiar with the scientific method steps, it's useful to see how each step could work with a real-life example.

Say, for instance, that researchers set out to discover what the relationship is between psychotherapy and anxiety.

• Step 1. Make an observation: The researchers choose to focus their study on adults ages 25 to 40 with generalized anxiety disorder.
• Step 2. Ask a question: The question they want to answer in their study is: Do weekly psychotherapy sessions reduce symptoms in adults ages 25 to 40 with generalized anxiety disorder?
• Step 3. Test your hypothesis: Researchers collect data on participants' anxiety symptoms. They work with therapists to create a consistent program that all participants undergo. Group 1 may attend therapy once per week, whereas group 2 does not attend therapy.
• Step 4. Examine the results: Participants record their symptoms and any changes over a period of three months. After this period, people in group 1 report significant improvements in their anxiety symptoms, whereas those in group 2 report no significant changes.
• Step 5. Report the results: Researchers write a report that includes their hypothesis, information on participants, variables, procedure, and conclusions drawn from the study. In this case, they say that "Weekly therapy sessions are shown to reduce anxiety symptoms in adults ages 25 to 40."

Of course, there are many details that go into planning and executing a study such as this. But this general outline gives you an idea of how an idea is formulated and tested, and how researchers arrive at results using the scientific method.