5.0 Research design Flashcards
Outline the steps to formulate a research problem (4)
Idea emerges
Brainstorm
Review literature
Identify variables
Research problem formulated
What is a research design?
The physical ‘doing’ part of the research process (e.g. sampling, data collection, data analysis).
Independent variable
The variable that is assumed to cause or influence the dependent variable(s) or outcome. The independent variable is manipulated in experimental research to observe its effect on the dependent variable(s). It is sometimes referred to as the treatment variable.
i.e. factor influencing the outcome being studied,
Dependent variable
The variable presumed within the research hypothesis to depend on (be caused by) another variable (the independent variable); it is sometimes referred to as the outcome variable.
i.e. result or outcome being studied.
Internal validity
The extent to which the outcome of a study can be attributed to the cause (Independent variable); also refers to the accuracy of the findings.
(Refers to the extent to which changes in the dependent variable (the observed effects) can be attributed to the independent variable rather than to extraneous variables.)
External validity
The extent to which the findings can be generalised beyond the sample; can the results be replicated with other samples.
(Refers to the degree to which the results of a study are generalisable beyond the immediate study sample and setting to other samples and settings.)
True or false. Internal validity is a prerequisite for external validity
True
What are the observational research designs?
Cross sectional studies
Case control studies
Cohort studies
(Researcher observes what occurs)
What are the experimental research designs?
RCTs
Quasi experimental designs
(Researcher intervenes to change the situation and watches what happens)
Cross-sectional study is aka
Prevalence study
A cross-sectional study provides …
Provide a snapshot of frequency and characteristics of a health condition/state among a population at a point in time.
Most common type of obsevational study. Most likely when assessing prevalence of a disease. Provides snapshot - one point in time. No follow up. e.g census survey.
True or false. In cross-sectional studies, ,measurement of exposure and outcome occur simultaneously among population of interest.
True
A cohort is…
a group that has something in common who are followed or studied over time
A cohort study
Commonly, a researcher studies the development of a particular health outcome or disease state.
Participants do not have the disease when recruited.
Then participants are classified according to whether they have one or more explanatory variables hypothetically related to the outcome. E.g. 2 groups - exposed smokers and unexposed non-smokers.
Then studied overtime to determine who develops the outcome of interest (e.g. lung cancer)
Can be cross-sectional (one point in time, or sequences of time points) or longitudinal (over long time periods).
Can be used to examine relationships retrospectively (more bias) and prospectively (more costly).
Can determine incidence e.g. new cases of COVID-19.
Case-control
Retrospective study design
Compares the personal characteristics and exposures of individuals with and without the disease/outcome of interest
Selects participants according to presence or absence of outcome of interest (DV, usually the disease); the exposure (IV) is determined retrospectively by careful examination of the participant’s history
Is a case-control study retrospective or prospective?
Retrospective - look back to identify risk factors for the outcome
In a case-control study who are the cases and who are the controls?
Cases = those who exhibit the outcome
Controls = those with similar characteristics but who do not exhibit the outcome
Note often have many more controls than cases.
Cases = outcome present Controls = outcome absent
Exposure present, exposure absent
Steps in a case control study (4)
- Identify cases
- Select controls which may be matched to the cases
- Measure exposure or risk factors of interst
- Compare the presence or absence of exposure in cases and controls
Steps in a prospective cohort study (3)
- Identify exposed and unexposed cohort groups
- During follow up period, identify diseased subjects (incident cases)
- Analyse differences (i.e. incidence or relative risk) among cohort exposed and cohort unexposed.
Steps in a retrospective cohort study (3)
- Identify exposed and unexposed cohort groups
- Identify diseased subjects by interview or written records
- Analyse differences (i.e. incidence or relative risk) among cohort exposed and cohort unexposed.
Pyramid of evidence - top to bottom
RCTs
Prospective cohort
Retrospective cohort
Case-control
Cross-sectional
Case series
Fewer threats to internal validity at the top.
Less bias –> more bias
Randomised controlled trials
Gold standard for testing cause and effect relationships in clinical research. Use when you want to determine effectiveness.
- Participants are randomly assigned to the experimental and control groups so that any pre-intervention differences are meausured/controlled.
- Intervention introduced to treatment group and outcome variable is measured again to see whether it has changed.
Control group gets no experimental treatment but is also measured for comparison purposes.
- Difference between the 2 groups at post-test reflects whether a causal link actually exists between explanatory and outcome variables.
True or False. Experimental study designs can establish cause and effect between the IV and DV.
True