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Health Research Study Designs

Trials in research are systematic investigations designed to test hypotheses, evaluate the effectiveness of interventions, and gather data to support or challenge specific outcomes. Trials typically involve a structured process where participants, treatments, or conditions are carefully controlled and monitored. 

Why are they important?

Trials can:

  • Help determine whether a new drug, therapy, or medical device is safe and works as intended before it is widely used.
  • Compare new interventions against standard treatments or placebos to see which is more effective.
  • Ensure compliance with regulatory bodies. For example, the Therapeutic Goods Administration (TGA) in Australia requires clinical trial data to approve new medical products.

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A clinical trial is a type of research study that tests new medical treatments, interventions, or drugs on human participants to evaluate their safety, effectiveness, and potential side effects. These trials follow strict protocols and are often conducted in phases to ensure thorough evaluation.

Requirements

  • Time requirements can vary depending on the trial phase, objectives, sample size, and the time needed to observe outcomes.
    • Short-term trials may take 1-5 years, while long-term trials can last over 10 years.
  • Small trials (e.g., <100 participants) may require a small team (5-10 researchers), while large-scale trials (e.g., 10,000+ participants) may need a larger, multidisciplinary team, including clinicians, researchers, and statisticians.
  • Follow Good Clinical Practice (GCP) guidelines and relevant reporting standards like CONSORT.
  • Obtain ethics approval and ensure participants provide informed consent before enrollment. 

How to do a clinical trial

  1. Develop a research question
  2. Search the literature
    1. You may need assistance from a librarian
  3. Develop the study methodology
    1. Consider target population, recruitment methods, sampling methods, and inclusion/exclusion criteria.
  4. Obtain approval 
  5. Design the Protocol: Write a detailed protocol, including objectives, methods, and outcome measures.
  6. Obtain funding
  7. Obtain consent
  8. Recruit participants: Use clear inclusion/exclusion criteria to select participants.
  9. Collect Data Gather baseline data, then administer the intervention and follow up with participants at set intervals.
  10. Monitor and ensure safety
  11. Analyse data
    1. You may need assistance from a biostatistician
  12. Write the research
  13. Publish your research

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RCTs are prospective studies which test the effectiveness of a new intervention --- such as a new drug, lifestyle intervention, or medical device. Importantly, these interventions are randomly allocated to the participants, reducing potential bias.  Although RCTs are the 'gold standard' for measuring effectiveness, they are resource-intensive and the findings are not always generalisable

 

Requirements:

  • Time requirements can vary depending on the trial phase, objectives, sample size, and the time needed to observe outcomes.
  • The size of your team depends on the study scale, ranging from 5–10 researchers for small studies to larger teams for big trials.
  • Follow Good Clinical Practice (GCP) guidelines and relevant reporting standards like CONSORT.
  • Obtain ethics approval and ensure participants provide informed consent before enrollment. 

How to conduct an RCT

  1. Develop a research question
    Formulate a focused research question that justifies the need for a randomised controlled trial design. The question should evaluate the effectiveness of an intervention (e.g., a drug, therapy, or behavior change) compared to a control group.
  2. Search the literature
    1. You may need assistance from a librarian
  3. Develop the study methodology
    1. Consider target population, recruitment methods, sampling methods, and inclusion/exclusion criteria.
    2. Plan how participants will be randomly assigned to intervention or control groups (simple randomisation, block randomisation, stratified randomisation, etc.).
  4. Obtain approval 
  5. Design the Protocol: Write a detailed protocol, including objectives, methods, and outcome measures.
  6. Obtain funding
  7. Obtain consent
  8. Recruit Participants: Use clear inclusion/exclusion criteria to select participants.
  9. Collect Data Gather baseline data, then administer the intervention and follow up with participants at set intervals.
  10. Monitor and Ensure Safety: Continuously monitor participants for safety and adverse effects
  11. Analyse data
    1. You may need assistance from a biostatistician
  12. Write the research
  13. Publish your research

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A non-randomised trial is a type of research study in which participants are not randomly assigned to different treatment groups. Instead, participants receive treatments based on pre-existing conditions, preferences, or other factors. These trials are often used when randomisation is not feasible or ethical, and they still aim to assess the effectiveness and safety of interventions.

Requirements:

  • Can range from a few months to several years, depending on the intervention, data collection, and analysis.
  • Team size can vary from small (3-5 researchers) for pilot studies to larger teams for more extensive research.
  • Requires ethics approval and informed consent from participants to ensure ethical standards are met.
  • Follow Good Clinical Practice (GCP) guidelines and relevant reporting standards like CONSORT.
  • Obtain ethics approval and ensure participants provide informed consent before enrollment. 

How to do a non-randomised trial

  1. Develop a research question
    Formulate a focused research question to assess the effectiveness of an intervention, with clear comparison between an intervention group and a control group.

  2. Search the literature
    1. You may need assistance from a librarian
  3. Develop the study methodology
    1. Define your target population, eligibility criteria, and recruitment methods.
    2. Choose a comparison (control) group that closely matches the intervention group in terms of key characteristics.
  4. Obtain approval 
  5. Design the Protocol: Write a detailed protocol, including objectives, methods, and outcome measures.
  6. Obtain funding
  7. Obtain consent
  8. Recruit Participants: Use clear inclusion/exclusion criteria to select participants.
  9. Collect Data Gather baseline data, then administer the intervention and follow up with participants at set intervals.
  10. Monitor and ensure safety
  11. Analyse data
    1. You may need assistance from a biostatistician
  12. Write the research
  13. Publish your research

Recommended resources:

A crossover clinical trial is a research design in which participants receive multiple interventions in a sequential manner. In a crossover trial, each participant acts as their own control by receiving both the treatment and the control intervention, typically separated by a washout period to avoid carryover effects. This design is often used when comparing two or more treatments to determine their relative effectiveness. 

Requirements

  • The trial can range from several months to years, depending on the number of interventions tested, washout periods, and follow-up requirements.
  • The research team size can range from small (3-5 researchers) for pilot trials to larger teams for more complex crossover designs.
  • Follow Good Clinical Practice (GCP) guidelines and relevant reporting standards like CONSORT.
  • Obtain ethics approval and ensure participants provide informed consent before enrollment. 

How to do a crossover trial

  • Develop a research question
    Define a focused research question that justifies the use of a crossover design. The question should address comparisons between two or more treatments.
  • Search the literature
    1. You may need assistance from a librarian
  • Develop the study methodology
    1. Identify the target population, inclusion/exclusion criteria, and how to manage potential confounding factors.
    2. Plan the sequence of treatments, ensuring an appropriate washout period between them to avoid carryover effects.
  • Obtain approval 
    Submit the study protocol to an ethics committee. Highlight the need for participant safety, informed consent, and details on the washout periods between treatments.
  • Design the Protocol: Write a detailed protocol, including objectives, methods, and outcome measures.
  • Obtain funding
  • Obtain consent
  • Recruit Participants: Use clear inclusion/exclusion criteria to select participants.
  • Collect Data: Gather baseline data, then administer the intervention and follow up with participants at set intervals.
  • Monitor and ensure safety
  • Analyse data
    1. You may need assistance from a biostatistician
  • Write the research
  • Publish your research
Example
Ellis, R. J., et al. (2009). Smoked medicinal cannabis for neuropathic pain in HIV: a randomized, crossover clinical trial. Neuropsychopharmacology, 34(3), 672–680. 

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A cluster randomised controlled trial (cRCT) is a research design where groups, or clusters, of participants (such as schools, hospitals or communities) are randomly assigned to either the intervention or control group, rather than individual participants. This design is useful when randomising individuals is not practical or when the intervention is delivered at the group level. 

Requirements:

  • The trial can last from several months to years, depending on the number of clusters, interventions, and follow-up requirements.
  • The team size can range from small (3-5 researchers) for pilot studies to larger teams for more complex trials involving multiple clusters.
  • Follow Good Clinical Practice (GCP) guidelines and relevant reporting standards like CONSORT.
  • Obtain ethics approval and ensure participants provide informed consent before enrollment. 

How to do a cRCT

  1. Develop a research question
    Formulate a clear research question that justifies the use of a cluster design. The question should compare the effectiveness of interventions at the group level..

  2. Search the literature
    1. You may need assistance from a librarian
  3. Develop the study methodology
    1. Define the target population and decide on the clustering criteria (e.g., schools, hospitals or communities etc.). Develop inclusion/exclusion criteria and identify potential confounders to address in the analysis.
  4. Obtain approval 
    Submit the study protocol to an ethics committee. Highlight the need for participant safety, informed consent, and details on the washout periods between treatments.
  5. Design the Protocol: Write a detailed protocol, including objectives, methods, and outcome measures.
  6. Obtain funding
  7. Obtain consent
  8. Recruit Participants: Use clear inclusion/exclusion criteria to select participants.
  9. Collect Data: Gather baseline data, then administer the intervention and follow up with participants at set intervals.
  10. Monitor and ensure safety
  11. Analyse data
    1. You may need assistance from a biostatistician
  12. Write the research
  13. Publish your research

Recommended resources:

A factorial trial is a research design that tests the effects of two or more interventions simultaneously by combining them in different ways. Participants are randomly assigned to different combinations of treatments or conditions, allowing researchers to study both the individual effects of each intervention and any potential interactions between them. 

Requirements

  • The trial duration can range from several months to years, depending on the number of interventions, follow-up periods, and the complexity of the design.
  • Requires a multidisciplinary team, typically including 3-5 researchers for simpler designs, or larger teams for complex trials with multiple factors and statistical analysis.
  • Follow Good Clinical Practice (GCP) guidelines and relevant reporting standards like CONSORT.
  • Obtain ethics approval and ensure participants provide informed consent before enrollment. 

How to do a factorial trial

  1. Develop a research question
    Formulate a clear research question that justifies the use of a factorial design. The question should explore the effects of multiple interventions, either individually or in combination, and how they interact..
  2. Search the literature
    1. You may need assistance from a librarian
  3. Develop the study methodology
    1. Define the target population and ensure the interventions are suitable for a factorial design. Determine the factors (e.g., treatments, interventions) to be tested and how they will be combined. Decide on the number of levels for each factor (e.g., low and high doses, treatment vs. no treatment).
  4. Obtain approval 
    Submit the study protocol to an ethics committee. Highlight the need for participant safety, informed consent, and details on the washout periods between treatments.
  5. Design the Protocol: Write a detailed protocol, including objectives, methods, and outcome measures.
  6. Obtain funding
  7. Obtain consent
  8. Recruit Participants: Use clear inclusion/exclusion criteria to select participants.
  9. Collect Data: Gather baseline data, then administer the intervention and follow up with participants at set intervals.
  10. Monitor and ensure safety: 
  11. Analyse data
    1. You may need assistance from a biostatistician
  12. Write the research
  13. Publish your research
Example
Day, L., et al. (2002). Randomised factorial trial of falls prevention among older people living in their own homes. BMJ (Clinical research ed.), 325(7356), 128.

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