Research Designs/Study Designs

Research design is a “blueprint” for how a research study is to be completed. It specifies the methods and procedures for measuring, collecting, and analyzing data. The type of design applied depends on the type of research, time available, economic considerations, and geographical area to be covered.

Here are the most common research designs discussed in the sources:

1. Experimental Study Design:

• • The researcher introduces an intervention (the ’cause’) and observes its impact on the population.
  • After-only design: The researcher studies the impact of an intervention on a population that has already been exposed to it. Baseline information is often based on recall or existing records.
  • Before-and-after design: The researcher establishes a ‘before’ observation before introducing an intervention and then takes an ‘after’ observation to determine the intervention’s impact.
  • Control group design: The researcher selects two groups, one that receives an intervention and one that does not, in order to compare the effects. Any differences in the dependent variable(s) are attributed to the intervention.
  • General Characteristics: Includes direct manipulation of independent variables, examination of their effects on dependent variables, testing of hypotheses, control of extraneous variables, and generation of empirical findings with internal and external validity.
    • Advantages: Allows control of the situation, identification of cause-and-effect relationships, and distinction between placebo and treatment effects. Provides the highest level of evidence for single studies.
    • Disadvantages: Can be artificial, may not generalize well to the real world, may alter participants’ behaviors, can be costly, and may not be suitable for all research problems.

1. 2. Cross-Sectional Study Design:

• • Utilizes different groups of people who differ in the variable of interest but share other characteristics.
  • Characteristics: Researchers record present information but do not manipulate variables, takes place at a single point in time, describes characteristics in a population, and does not determine cause-and-effect relationships. Allows examination of numerous things at once.
    • Advantages: Provides a clear ‘snapshot’ of the outcome and associated characteristics at a specific time, focuses on existing differences, collects data at one point in time, is relatively inexpensive and quick to conduct.
    • Disadvantages: It can be difficult to find very similar subjects, results are static and time-bound, cannot establish cause-and-effect relationships, and may have differing results with different time frames.

3. Longitudinal Research Design:

• • Involves a series of sample measurements taken over a period of time, examining behavior of a respondent/group and noting changes.
  • Types: Panel studies (same sample over time) and trend studies (different samples from the same population over time).
    • Advantages: Facilitates analysis of the duration of a particular phenomenon, gets close to causal explanations, permits measurement of differences in a variable over time, and allows prediction of future outcomes.
    • Disadvantages: Data collection methods may change over time, maintaining sample integrity can be difficult, it can be difficult to show more than one variable at a time, and may need qualitative research data to explain fluctuations.

4. Case Study/Case Report Designs:

• • An in-depth study of behavior of a particular phenomenon.
  • Characteristics: Focuses on a single case, uses a variety of data collection methods, and has a strong link to practice and policy.
  • Advantages: Provides a deeper understanding of a phenomenon, has practical significance, and can be useful for unique situations.
  • Disadvantages: Findings may not be generalizable to the wider population, the researcher’s interpretation may be biased, it does not facilitate assessment of cause and effect, and vital information may be missing.

5. Case Control Study Design:

• • Observational study in which two existing groups differing in outcome are compared on the basis of some supposed causal attribute.
  • Often used to identify factors that may contribute to a medical condition by comparing subjects who have the condition (the “cases”) with similar patients who do not (the “controls”).

6. Retrospective and Prospective Studies:

• • A retrospective study looks back in time (e.g., reviewing past medical records).
  • A prospective study looks forward.

7. Qualitative vs. Quantitative Research Designs:

• • Qualitative research deals with phenomena that are difficult or impossible to quantify mathematically, focusing on beliefs, meanings, attributes, and symbols. It involves a narrative description of phenomenon as they are in naturally occurring settings.
  • Quantitative research deals with phenomena that are possible to quantify mathematically.

8. Cohort Study Design:

• • A cohort is a group of people who share a common characteristic or experience.
  • One or more samples (cohorts) are followed, and their status with respect to a disease/outcome is evaluated to determine which initial characteristics are associated with it.
    • Advantages: Measures potential causes before the outcome, can demonstrate the “causes” preceded the outcome, can use original or secondary data, and is easier and cheaper than a randomized controlled trial.
    • Disadvantages: Cohorts can be difficult to identify due to confounding and can take a long period of time.

1. 9. Randomized Controlled Trial (RCT):

• • The researcher randomly assigns participants into control and experimental groups.
  • In contrast to cohort studies, RCTs have a random assignment of samples.

10. Case Series/Clinical Series:

• • Descriptive study that follows a group of patients with a known exposure.
  • Results can generate hypotheses but no causal inferences should be made.

11. Correlation Study Design:

• • Determines whether two variables are correlated, meaning whether an increase or decrease in one variable corresponds to an increase or decrease in the other.
  • Types: Positive, negative, and zero correlation.
  • Important Note: Correlation does not imply causation.
  • Correlation values range from -1 to +1, with values close to +1 indicating strong positive correlation, values close to -1 indicating strong negative correlation, and values near zero indicating no correlation.

12. Comparative Study Design:

• • Examines two or more cases that are similar in some respects but differ in others.
  • The goal is to find out why the cases are different and to generalize the findings to groups where the cases came from.

These different research designs provide frameworks for answering a variety of research questions using various data collection and analysis methods.