 Cross-sectional design is one that evaluates or compares individuals, perhaps of different age groups, at the same point in time.

Cross-Sectional Approaches

 A longitudinal design follows the same subjects over time. 

Longitudinal Studies 

- Studies are costly to carry out
- Require great patience and continuity leadership in the research program
- Researchers must live with design mistakes made years earlier or put up with outmoded research and assessment methods
- Participants sometimes drop out of longitudinal studies
   - One must demonstrate that the retained participants are representative of those that started the study

Variations and Problems with Cross-Sectional and Longitudinal Approaches 

A developmental psychologist wants to study how problem-solving skills change over the lifespan. The psychologist recruits a group of 20-year-olds, a group of 40-year-olds, and a group of 60-year-olds. All participants are given the same problem-solving test during the same month. Which research design does this study exemplify?

Another way of classifying research studies is by considering whether the studies are cross-sectional or longitudinal in nature.

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There are many methods of research utilized in Clinical Psychology. 

Methods of Research in Clinical Psychology

Trull , T. J., &amp; Prinstein , M. J. (2013). Research Methods in Clinical Psychology . In Clinical Psychology (Eighth, pp. 93–124). Textbook, Wadsworth Cengage Learning . 

Clinical Psychology Eighth Edition 

Spielman, R. M., Jenkins, W. J., & Lovett, M. D. (2020, April 22). Psychology (2nd ed.). OpenStax. https://openstax.org/books/psychology-2e/pages/1-introduction

OpenStax Psychology (2nd ed.) Textbook

Regarding epidemiology, the expectation is that analyzing the distribution of cases in a community or region and uncovering the distinguishing characteristics of the affected individuals or groups will teach us something about the causes of a particular disease and the methods by which it spreads. Epidemiological methods can also be quite important in identifying groups of individuals who are at risk.

Epidemiological Methods 

Cross-Sectional vs. Longitudinal Approaches 

Here, participants who can be divided into specific populations (e.g. schizophrenic vs. normal) are assigned as groups to each experimental condition. In this way, variables such as psychosis or normality are not manipulated or induced by the investigator. Instead, they are correlated with the experimental condition. 

Mixed Designs 

Various research methods commonly used by clinical psychologists each have different strengths and weaknesses.

Strengths and Weaknesses of Research Methods

Quantitative research relies on measuring variables using a numerical system, analyzing these measurements using any of a variety of statistical models, and reporting relationships and associations among the studied variables. The goal of gathering quantitative data is to understand, describe, and predict the nature of a phenomenon, particularly through the development of models and theories.

Quantitative Methods

Alderfer, M. A., & Sood, E. (2016). Using qualitative research methods to improve clinical care in pediatric psychology. Clinical Practice in Pediatric Psychology, 4(4), 358-361. doi:https://doi.org/10.1037/cpp0000164

Using qualitative research methods to improve clinical care in pediatric psychology

Qualitative research in clinical care settings involves the communication between a patient (and sometimes their family members) and their doctor in order to comprehend a patient's symptoms. Therefore, qualitative research in clinical psychology is extremely valuable and helpful in the diagnosis and treatment of individuals. 

Qualitative Methods

The most basic and pervasive of all research methods is observation.  Experimental, case study, and naturalistic approaches all involve making observations of what someone is doing or has done. 

- Unsystematic Observation
- Naturalistic Observation
- Controlled Observation 


Observation in Psychology 

Correlational research is a widespread type of non-experimental research in which an investigator measures two variables—either continuous or categorical—and evaluates the statistical relationship (correlation) between them. Crucially, the researcher does this with little to no effort to control extraneous variables or manipulate an independent variable. It is often chosen when a relationship is not believed to be causal, or when exploring causal relationships where manipulating the independent variable is impossible, impractical, or unethical. By utilizing this strategy, researchers can achieve two fundamental scientific goals: describing the strength and direction of the relationship between the variables, and predicting scores on one variable based on the other using a statistical technique called regression.

Correlational Research

In the psychological sciences, you can conduct basic research and applied research. 

Basic research is theoretical research that explains why and how psychological processes occur 

Example of basic research: How do different parts of the brain process emotions?

Applied research is research that aims to solve a problem and aims to produce immediate, practical outcomes. 

Example of applied research: Testing a specific psychotherapy technique for treating depression

Basic research vs. applied research

Single-subject research, frequently referred to as small-$$n$$ design (where $$n$$ represents the statistical symbol for sample size), is a quantitative methodology that involves studying a small number of participants and focusing closely on each individual's behavior. Despite its name, this approach typically investigates between two and ten participants rather than just one. Serving as a crucial alternative to group research, particularly in applied areas of psychology, single-subject research seeks to comprehend objective behavior by utilizing strict experimental manipulation and control to collect highly structured data that is analyzed using quantitative techniques.

Single-Subject Research

Utilized to determine cause-effect relationships among events. 

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