Study Design in Research
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What is a key factor in determining the appropriate study population for a trial?

  • Specific inclusions and exclusions based on scientific and safety considerations (correct)
  • Recruitment of participants solely based on convenience
  • Random selection of participants irrespective of their health status
  • Generalizability of results to unrelated populations

Which criterion is NOT important when selecting participants for a study?

  • Risk of the outcome being studied
  • Participants' enthusiasm for the study (correct)
  • Presence of conditions that render the drug contraindicated
  • Likelihood of compliance with treatment

How does the number of inclusion/exclusion criteria affect a study's generalizability?

  • Increased criteria improves generalizability
  • Generalizability is only impacted by sample size
  • The number of criteria has no effect on generalizability
  • Increased criteria decreases generalizability (correct)

What is meant by the term 'reference population' in the context of a study?

<p>The larger group to which study results will apply (B)</p> Signup and view all the answers

Which factor does NOT enhance the likelihood of successful recruitment of a study population?

<p>Targeting a highly specific population with strict criteria (D)</p> Signup and view all the answers

What type of study involves the investigator intervening to assess the effectiveness of prevention or treatment?

<p>Experimental studies (B)</p> Signup and view all the answers

In which type of trial would agents be given to healthy or high-risk individuals to prevent disease occurrence?

<p>Prevention trial (B)</p> Signup and view all the answers

Which phrase best describes the ethical burdens present in human experimental research compared to lab studies?

<p>Human experimental research often involves more ethical dilemmas. (A)</p> Signup and view all the answers

What was a key ethical issue highlighted in the history of experimental studies, specifically referred to as the Monster study?

<p>Inducing stuttering through belittling (A)</p> Signup and view all the answers

Which type of trial allocates treatment to communities rather than individual participants?

<p>Community (cluster) trial (D)</p> Signup and view all the answers

In experimental studies, what is typically expected regarding the population level effect of the intervention?

<p>Small effect (C)</p> Signup and view all the answers

In a therapeutic (clinical) trial, what is the primary goal regarding participants?

<p>To treat or cure a disease (D)</p> Signup and view all the answers

Which of the following is NOT a characteristic of observational studies?

<p>Usually expects a small population effect (D)</p> Signup and view all the answers

What is a key feature of experimental studies?

<p>Exposure status is assigned by the investigators (D)</p> Signup and view all the answers

In the context of clinical trials, what does the term 'randomized' indicate?

<p>Exposure is assigned without bias (D)</p> Signup and view all the answers

What was the primary contribution of James Lind in clinical trials?

<p>Conducting the first recorded randomized clinical trial (C)</p> Signup and view all the answers

Which method is associated with reducing confounding in study groups?

<p>Matching cases to controls based on exposure (D)</p> Signup and view all the answers

What is the defining feature of experimental studies compared to observational studies?

<p>Random assignment to study groups (B)</p> Signup and view all the answers

Which process is NOT a hallmark of clinical trials?

<p>Self-selection of participants into groups (B)</p> Signup and view all the answers

What was one of the key findings in Edward Jenner's experiment?

<p>Proof that cowpox could prevent smallpox (C)</p> Signup and view all the answers

What is the primary purpose of informed consent in a trial?

<p>To provide a clear explanation of research goals and methods. (C)</p> Signup and view all the answers

Which method is an example of random assignment in a clinical trial?

<p>Using a computer to generate random numbers. (B)</p> Signup and view all the answers

What is a potential problem with non-random assignment in a trial?

<p>It can lead to biased group assignment. (B)</p> Signup and view all the answers

How does randomization contribute to the confidence of trial results?

<p>It minimizes inaccurate results caused by confounding. (C)</p> Signup and view all the answers

What is the ultimate goal of randomization in clinical trials?

<p>To create two groups that are identical except for treatment. (D)</p> Signup and view all the answers

What can happen if randomization does not work effectively in a study?

<p>Differences between groups may be due to sampling error. (D)</p> Signup and view all the answers

What characteristic does randomization ideally create among study groups?

<p>Similarity in all factors except the treatment received. (B)</p> Signup and view all the answers

What is a key requirement for randomization to be effective in a study?

<p>The study must be large enough to minimize confounding effects. (D)</p> Signup and view all the answers

What is one consequence of noncompliance in a randomized controlled trial?

<p>It makes treatment and control groups more alike. (B)</p> Signup and view all the answers

What is a major strength of randomized controlled trials (RCTs)?

<p>They demonstrate causal relationships with high levels of confidence. (B)</p> Signup and view all the answers

What is a cluster randomized trial particularly advantageous for?

<p>Reducing the risk of contamination. (D)</p> Signup and view all the answers

What does the term 'double-blind' refer to in a study?

<p>Both the study participant and the investigator do not know the treatment assignment. (C)</p> Signup and view all the answers

What does the analysis in a randomized controlled trial include?

<p>Setting up a 2x2 table for incidence rates in treatment and comparison groups. (C)</p> Signup and view all the answers

What is a potential limitation of randomized controlled trials?

<p>They may have limited external validity. (D)</p> Signup and view all the answers

In a triple-blind study, who does not know the treatment assignment?

<p>The study participant, the investigator administering the treatment, and the investigator monitoring effects. (D)</p> Signup and view all the answers

What is a primary goal of using randomization in studies?

<p>To make sure the groups are as similar as possible on important characteristics. (B)</p> Signup and view all the answers

In cross-over trials, what is the main methodological characteristic?

<p>Each person serves as their own control by switching between treatments. (A)</p> Signup and view all the answers

What common issue can arise in randomized controlled trials due to different levels of compliance?

<p>Bias towards the null. (D)</p> Signup and view all the answers

Why might a placebo not always be ethically acceptable in a study?

<p>Placebos can create a false sense of security compared to current standard care. (A)</p> Signup and view all the answers

Why might some interventions be managed at the cluster level rather than individually?

<p>They are more convenient to implement at the group level. (D)</p> Signup and view all the answers

What is the 'placebo effect'?

<p>Participants experience improvements due to the power of suggestion. (A)</p> Signup and view all the answers

What does compliance in a study refer to?

<p>The extent to which participants adhere to the study protocol. (B)</p> Signup and view all the answers

Which of the following is a potential issue that can arise from deviations in study protocols?

<p>Contamination between treatment and control groups. (B)</p> Signup and view all the answers

When is blinding not feasible in a study?

<p>When participants can guess their treatment based on experience. (A)</p> Signup and view all the answers

Flashcards

Experimental Study

A study where researchers actively manipulate the exposure variable to see its effect on the outcome.

Observational Study

A study where researchers observe naturally occurring exposures and outcomes without direct intervention.

Matching

A method used in observational studies to create groups that are as similar as possible in terms of potentially confounding factors after assigning participants to exposure/outcome groups.

Confounding Adjustment

Similar to randomization in experimental studies, but used in observational studies. It aims to create groups with similar characteristics after assigning participants to exposure/outcome groups.

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Randomized Controlled Trial (RCT)

A type of experimental study where participants are randomly assigned to either receive the intervention (exposure) or not.

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Exposure Variable

The variable researchers manipulate to see its effect on the outcome.

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Outcome Variable

The variable researchers measure to see if it's affected by the exposure.

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Confounding Factors

Factors that could influence the outcome variable but are not the exposure of interest. They need to be controlled for in observational studies.

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Prevention Trial

An experimental study designed to evaluate the effectiveness of an agent in preventing a disease in healthy or high-risk individuals. It aims to determine if the agent can reduce the likelihood of developing the disease.

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Therapeutic (Clinical) Trial

An experimental study designed to evaluate the effectiveness of a treatment or agent in curing or treating an existing disease. It aims to determine if the agent improves the condition or outcome of individuals with the disease.

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Individual Trial

A type of experimental study where the treatment or intervention is allocated to individual participants. It allows for the study of the effectiveness of different treatment options within a group of individuals.

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Community (Cluster) Trial

A type of experimental study where the treatment or intervention is allocated to entire communities or groups. It allows for the study of the impact of interventions at a population level.

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Study Population

The group of individuals who are eligible to participate in a research study.

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Inclusion and Exclusion Criteria

Specific characteristics or factors used to decide who can or cannot participate in a research study.

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Generalizability

The extent to which the results of a research study can be applied to a broader group of people.

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Recruitment of Study Population

The process of finding and recruiting participants for a research study.

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Reference Population

The group of individuals to whom the results of a research study are expected to apply.

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Blinding

Method of ensuring that participants and/or study investigators have no knowledge of whether a study participant has been assigned to the treatment or comparison group.

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Single-blind

Blinding where the study participant does not know whether they are receiving treatment or no treatment.

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Double-blind

Blinding where neither the study participant nor the study investigator knows who is receiving treatment or no treatment.

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Triple-blind

Blinding where neither the study participant nor the study investigator administering the treatment nor the study investigator monitoring the effects of the treatment knows who is receiving treatment or no treatment.

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Placebo

A method of blinding that uses a treatment that looks and feels like the real treatment but has no active ingredients.

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Placebo Effect

The phenomenon where participants assigned to placebo groups improve because they are told they will.

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Random assignment

Each participant has an equal chance of receiving the treatment or control. This is achieved through methods like coin flips or computer-generated randomization.

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Randomization

A technique used to ensure that groups in a study are similar in terms of potential confounders. It aims to balance these factors across groups.

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Stratified randomization

A method of randomization that divides the study population into subgroups based on characteristics like age or sex. Then, participants are randomly assigned to treatment or control within each subgroup.

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Ultimate goal of randomization

The only difference between study groups should be the treatment. Randomization helps achieve this by balancing other factors.

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When randomization doesn't work

Occurs when randomization doesn't effectively distribute confounders evenly between groups. This can lead to inaccurate results.

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Chance differences due to sampling error

Sampling error is more likely to occur when the study sample is small. This can lead to chance differences between groups.

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Noncompliance

A situation where participants in a study do not follow the assigned treatment plan, either by receiving the intervention when they were supposed to be in the control group or vice versa.

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Impact of Noncompliance

When noncompliance occurs, it makes the treatment and control groups more similar, potentially masking any real differences between them.

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Crossover Trial

A study where participants are randomly assigned to receive either the treatment or control first, and then switch to the other after a certain period. Each participant acts as their own control.

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Cluster Randomized Trial

A type of experimental study where the intervention or treatment is assigned at the group level (e.g., a community or school), rather than individual participants.

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Descriptive Analysis

A method of data analysis focused on summarizing and describing patterns in the data, including factors such as participant characteristics and outcome measures.

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2x2 Table

A way of summarizing data using a table that shows the number of individuals with and without the outcome in both the treatment and control groups.

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Incidence Rate

A measure of how often an event occurs in a specific group over a certain period of time.

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Relative Comparison

A measure that compares the incidence rates between the treatment and control groups, indicating the relative effect of the intervention.

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Study Notes

Study Design

  • Making groups similar: Groups are made as similar as possible to account for confounding variables. This is similar to randomization in experimental studies, but the only difference is exposure (intervention) status. Outcome groups are made similar in other factors.
  • Matching: Matching cases to controls is used to make outcome groups similar in other factors. The only difference between groups is outcome status.
  • Observational Studies: Researchers collect and analyze data on participants as they naturally divide themselves by exposure and outcome.
  • Experimental Studies: Researchers intentionally intervene and control the exposure variable to see how it influences the outcome.
  • Key feature: In experimental studies, exposure status, and other conditions of the study are controlled by the researchers.
  • Intervention studies: Researchers assign participants to groups, one group receives the exposure of interest, and the other does not. The groups are then observed over time.
  • Clinical Trials: Intervention studies are sometimes called clinical trials.
  • Randomized Controlled Trials (RCTs): Clinical trials can be randomized controlled trials, where the exposure (treatment/intervention) is randomly assigned to participants.

History of Randomized Clinical Trials

  • James Lind: Scottish naval surgeon who conducted an early randomized experiment with scurvy victims.
  • Edward Jenner: Conducted an experimental inoculation study, but neither randomized nor control group.

Experimental Studies Emulating Lab Experiments

  • Lab experiments regulate aspects like genetic similarity, environment, and dosage, with the only difference being the test variable (chemical).
  • Human experimental research emulates lab practices but doesn't have the same level of control.
  • Ethical considerations are important for human research.

Types of Experimental Studies

  • Prevention trials: Agents are given to healthy or high-risk individuals to prevent disease occurrences (e.g., removing lead from soil preventing lead poisoning).
  • Clinical trials: Agents are given to diseased individuals to treat or cure disease (e.g., drugs for breast cancer treatment).

Study Population

  • Researchers specify study population characteristics (inclusion/exclusion criteria).
  • Generalizability: The extent to which the results can be applied to a broader population.
  • Reference populations: Study results can be applied to pre-defined reference populations.
  • Participants must give informed consent.
  • Consent includes understanding of procedures, benefits, risks, and the right to withdraw.
  • Random assignment of treatment/control groups is crucial to minimizing bias.

Minimizing Bias

  • Blinding (masking): Study participants and/or investigators are unaware of treatment/control group assignments to prevent bias.
  • Single-blind: Participants are unaware of group assignments.
  • Double-blind: Both participants and researchers are unaware.
  • Triple-blind: (Researchers, participants, and data analysts are unaware)
  • Placebos: Placebo treatments can be used as controls to prevent bias by participant expectations.

Analysis

  • Descriptive analysis: Check if randomization was effective by examining if confounding factors are evenly distributed in groups. Measures/statistics of association such as incidence rates are calculated.
  • Intention-to-treat analysis: Analyses of the outcomes in the original group assignments, intended to measure effectiveness of the treatment as intended.
  • Efficacy analysis: Directly compares treatment and control groups.
  • Cross-over trials: Participants switch between treatments over time acts as their own control group.

Strengths and Weaknesses of RCTs/Experimental Studies

  • Strengths: High confidence in causal relationships and control over exposure.
  • Weaknesses: Ethical limitations, external validity concerns, compliance, contamination (participants stray from designed protocols).

Cluster Randomized Trials

  • The basic approach is the same, but the unit of randomization is the cluster (group, community). Ex. Villages, schools, hospitals, etc.

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Description

This quiz covers key concepts in study design, including the differences between observational and experimental studies, matching, and how researchers control variables. It emphasizes the importance of creating similar groups and understanding intervention effects on outcomes.

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