If analytical, did the investigator determine the exposure? If observational, when was the outcome determined? In the next few pieces in the series, we will discuss various study designs in greater detail. National Center for Biotechnology Information , U.
Journal List Perspect Clin Res v. Perspect Clin Res. Priya Ranganathan and Rakesh Aggarwal 1. Author information Copyright and License information Disclaimer. Address for correspondence: Dr.
E-mail: moc. This is an open access journal, and articles are distributed under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike 4. This article has been cited by other articles in PMC. Abstract There are several types of research study designs, each with its inherent strengths and flaws. Keywords: Epidemiologic methods, research design, research methodology. Variable A variable represents a measurable attribute that varies across study units, for example, individual participants in a study, or at times even when measured in an individual person over time.
Exposure or intervention and outcome variables A large proportion of research studies assess the relationship between two variables.
Descriptive versus analytical studies Descriptive or nonanalytical studies, as the name suggests, merely try to describe the data on one or more characteristics of a group of individuals.
Directionality of study designs Based on the direction of inquiry, study designs may be classified as forward-direction or backward-direction. Classification of study designs Figure 1 depicts a simple classification of research study designs. Open in a separate window. Figure 1.
Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest. Centre for Evidence-Based Medicine. Study Designs. Support Center Support Center. Conditions necessary for determining causality:. Bachman, Ronet. Chapter 5, Causation and Research Designs. Chapter 11, Nonexperimental Research: Correlational Designs. Often used in the medical sciences, but also found in the applied social sciences, a cohort study generally refers to a study conducted over a period of time involving members of a population which the subject or representative member comes from, and who are united by some commonality or similarity.
Using a quantitative framework, a cohort study makes note of statistical occurrence within a specialized subgroup, united by same or similar characteristics that are relevant to the research problem being investigated, r ather than studying statistical occurrence within the general population. Using a qualitative framework, cohort studies generally gather data using methods of observation.
Cohorts can be either "open" or "closed. Healy P, Devane D. Evidence-Based Dentistry 7 : 51—52; Study Design Himmelfarb Health Sciences Library. Cross-sectional research designs have three distinctive features: no time dimension, a reliance on existing differences rather than change following intervention; and, groups are selected based on existing differences rather than random allocation. The cross-sectional design can only measure diffrerences between or from among a variety of people, subjects, or phenomena rather than change.
As such, researchers using this design can only employ a relative passive approach to making causal inferences based on findings. Hall, John. Paul J. Lavrakas, ed. Thousand Oaks, CA: Sage, , pp. Healthknowledge, Cross-Sectional Study. Descriptive research designs help provide answers to the questions of who, what, when, where, and how associated with a particular research problem; a descriptive study cannot conclusively ascertain answers to why.
Descriptive research is used to obtain information concerning the current status of the phenomena and to describe "what exists" with respect to variables or conditions in a situation. Chapter 5, Flexible Methods: Descriptive Research. Descriptive Research Methodologies. Powerpoint Presentation; Shuttleworth, Martyn. Descriptive Research Design , September 26, A blueprint of the procedure that enables the researcher to maintain control over all factors that may affect the result of an experiment.
In doing this, the researcher attempts to determine or predict what may occur. Experimental Research is often used where there is time priority in a causal relationship cause precedes effect , there is consistency in a causal relationship a cause will always lead to the same effect , and the magnitude of the correlation is great. The classic experimental design specifies an experimental group and a control group.
The independent variable is administered to the experimental group and not to the control group, and both groups are measured on the same dependent variable. Subsequent experimental designs have used more groups and more measurements over longer periods. True experiments must have control, randomization, and manipulation.
Chapter 7, Flexible Methods: Experimental Research. Research Methods by Dummies. Department of Psychology. Experimental Design. Experimental Research. Slideshare presentation. An exploratory design is conducted about a research problem when there are few or no earlier studies to refer to.
The focus is on gaining insights and familiarity for later investigation or undertaken when problems are in a preliminary stage of investigation. The goals of exploratory research are intended to produce the following possible insights:. Cuthill, Michael. Catalano, and D. The purpose of a historical research design is to collect, verify, and synthesize evidence from the past to establish facts that defend or refute your hypothesis.
It uses secondary sources and a variety of primary documentary evidence, such as, logs, diaries, official records, reports, archives, and non-textual information [maps, pictures, audio and visual recordings]. The limitation is that the sources must be both authentic and valid.
Savitt, Ronald. Chapter 16, Historical Research. A longitudinal study follows the same sample over time and makes repeated observations. With longitudinal surveys, for example, the same group of people is interviewed at regular intervals, enabling researchers to track changes over time and to relate them to variables that might explain why the changes occur.
Longitudinal research designs describe patterns of change and help establish the direction and magnitude of causal relationships. Measurements are taken on each variable over two or more distinct time periods. This allows the researcher to measure change in variables over time.
It is a type of observational study and is sometimes referred to as a panel study. This type of research design draws a conclusion by comparing subjects against a control group, in cases where the researcher has no control over the experiment. There are two general types of observational designs. In direct observations, people know that you are watching them. Unobtrusive measures involve any method for studying behavior where individuals do not know they are being observed.
An observational study allows a useful insight into a phenomenon and avoids the ethical and practical difficulties of setting up a large and cumbersome research project.
Atkinson, Paul and Martyn Hammersley. Norman K. Denzin and Yvonna S. Lincoln, eds. Qualitiative Research and Evaluation Methods. Chapter 6, Fieldwork Strategies and Observational Methods. Design of Observational Studies. New York: Springer, Understood more as an broad approach to examining a research problem than a methodological design, philosophical analysis and argumentation is intended to challenge deeply embedded, often intractable, assumptions underpinning an area of study.
This approach uses the tools of argumentation derived from philosophical traditions, concepts, models, and theories to critically explore and challenge, for example, the relevance of logic and evidence in academic debates, to analyze arguments about fundamental issues, or to discuss the root of existing discourse about a research problem. These overarching tools of analysis can be framed in three ways:. Chapter 4, Research Methodology and Design.
Washington, D. Et al. Abbas Tashakkori and Charles Teddle, eds. Neil J. Salkind, ed. It looks like you're using Internet Explorer 11 or older.
This website works best with modern browsers such as the latest versions of Chrome, Firefox, Safari, and Edge. If you continue with this browser, you may see unexpected results. The Conclusion Toggle Dropdown Appendices Introduction Before beginning your paper, you need to decide how you plan to design the study. General Structure and Writing Style The function of a research design is to ensure that the evidence obtained enables you to effectively address the research problem as unambiguously as possible.
Given this, the length and complexity of research designs can vary considerably, but any sound design will do the following things: Identify the research problem clearly and justify its selection, Review previously published literature associated with the problem area, Clearly and explicitly specify hypotheses [i.
Action Research Design Definition and Purpose The essentials of action research design follow a characteristic cycle whereby initially an exploratory stance is adopted, where an understanding of a problem is developed and plans are made for some form of interventionary strategy. What do these studies tell you? A collaborative and adaptive research design that lends itself to use in work or community situations. Design focuses on pragmatic and solution-driven research rather than testing theories.
When practitioners use action research it has the potential to increase the amount they learn consciously from their experience. The action research cycle can also be regarded as a learning cycle. Action search studies often have direct and obvious relevance to practice.
There are no hidden controls or preemption of direction by the researcher. Advantages: quick and cheap; only feasible method for very rare disorders or those with long lag between exposure and outcome; fewer subjects needed than cross-sectional studies.
Disadvantages: reliance on recall or records to determine exposure status; confounders; selection of control groups is difficult; potential bias: recall, selection. Cross-Sectional Survey A study that examines the relationship between diseases or other health-related characteristics and other variables of interest as they exist in a defined population at one particular time ie exposure and outcomes are both measured at the same time.
Advantages: cheap and simple; ethically safe. Disadvantages: establishes association at most, not causality; recall bias susceptibility; confounders may be unequally distributed; Neyman bias; group sizes may be unequal.
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