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Conducting Rigorous Research Seminar Workbook

5 Seminar Four

This session is protected time to work on the planning of your experimental trial and for the write up of your trial protocol. Based on this weeks lecture content you should now be able to add information about the specific randomisation strategy you plan to use.

5.1 Control Groups

5.1.1 Purpose

  • Minimize Bias: Randomization helps to ensure that each participant has an equal chance of receiving any treatment being studied. This minimizes selection bias, where certain characteristics of participants could influence their assignment to treatment groups, thus ensuring the groups are comparable at the outset.
  • Reduce Confounding Variables: By randomly assigning participants to treatment groups, the likelihood of confounding variables (factors other than the treatment itself that might affect the outcome) being evenly distributed among groups is increased. This allows researchers to better attribute any differences in outcomes to the treatment being studied.
  • Enhance Generalizability: Randomization increases the likelihood that the study sample is representative of the wider population, improving the generalizability of the findings.
  • Ensure Valid Statistical analysis: Randomization allows for the use of statistical methods that assume random assignment, enabling valid inference about the effectiveness of treatments.
  • Ethical Considerations: Randomization helps to ensure fairness in allocating treatments and reduces the risk of preferential treatment or discrimination, thus upholding ethical standards in research.

5.1.2 Components

  • Randomization Procedure: This is the method used to assign participants to different treatment groups. Randomization ensures that each participant has an equal chance of being assigned to any of the treatment groups, which helps to eliminate bias and ensure the groups are comparable at the start of the trial.
  • Allocation Concealment: This involves keeping the treatment assignments hidden from both the researchers and the participants until the moment of randomization. Concealment prevents selection bias and ensures that neither the researchers nor the participants can influence the assignment of treatments.
  • Implementation of Randomization: This encompasses the practical aspects of carrying out the randomization process, including the use of centralized randomization systems, allocation schedules, and ensuring adherence to the randomization protocol throughout the trial. Proper implementation ensures the integrity and validity of the randomization process.

5.1.3 Types

  • Simple Randomization:
    • Involves assigning participants randomly to different treatment groups.
    • Easy to implement but may not balance baseline characteristics evenly between groups, potentially leading to confounding. Stratified Randomization:
    • Divides participants into subgroups based on certain characteristics (e.g., age, gender, disease severity) and then applies randomization within each stratum.
    • Ensures balance in key prognostic factors across treatment groups, enhancing comparability and reducing bias.
  • Block Randomization:
    • Involves dividing participants into blocks and ensuring that each block contains an equal number of participants assigned to each treatment group.
    • Helps maintain balance in treatment allocation over time and prevents predictability of treatment assignments.
  • Stratified Block Randomization:
    • Combines features of both stratified and block randomization methods.
    • Participants are divided into subgroups (strata) based on specific characteristics (e.g., age, gender, disease severity).
    • Within each stratum, participants are further allocated to treatment groups using block randomization.
    • This method ensures balance not only within each subgroup but also across different strata, minimizing the impact of potential confounders and improving comparability between treatment arms.
    • Particularly useful when there are known prognostic factors that may influence treatment outcomes, allowing for more precise estimation of treatment effects within specific subgroups.

5.2 Useful information

SPIRIT guidelines (Table 1):

Staffordshire University Experimental Trial Protocol Template