Which of the following threats to internal validity is best controlled by using random assignment in experime… - GMCH Nursing Officer-2025

GMCH Nursing Officer-2025

Nursing Research & Statistics

Easy

Appeared in: GMCH Nursing Officer-2025

Explanation

Random assignment is the most effective method for controlling selection bias in experimental studies.
It ensures that every participant has an equal chance of being placed in either the experimental or control group.
This process distributes both known and unknown participant characteristics (like age, severity of illness, motivation) evenly across the groups.
As a result, the groups are comparable at the beginning of the study, which eliminates systematic baseline differences that could otherwise explain the results.

Option A: History refers to external events that occur during the study. Random assignment does not prevent these events from happening.
Option B: Maturation refers to natural changes in participants over time (e.g., healing, aging). Random assignment does not stop these natural processes.
Option D: The testing effect occurs when taking a pre-test affects performance on a post-test. Random assignment does not address this issue.

Visual 1: Flowchart: Depicting how a pool of participants is randomly assigned to a control group and an experimental group, resulting in two comparable groups.
Visual 2: Infographic: A table comparing the main threats to internal validity (History, Maturation, Selection Bias, Testing, Attrition) with their definitions and primary control methods.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Threats to Internal Validity in Experimental Research as background academic context rather than a clinical decision trigger.
Nurses must critically appraise research to ensure evidence-based practice. Understanding that random assignment controls for selection bias is key to identifying high-quality studies (like Randomized Controlled Trials or RCTs) whose results are more trustworthy.
When reading a study, a nurse should look for whether random assignment was used. Its presence increases confidence that the intervention, and not some other factor, caused the outcome.
What if? If a study on a new diabetes education program allowed patients to choose whether to join, more motivated patients might self-select into the program. This creates selection bias, and any improvement seen might be due to their motivation, not the program itself. Random assignment would prevent this by ensuring both motivated and unmotivated patients are in each group.

How to Approach the Question

First, identify the core concepts in the question: 'threats to internal validity' and 'random assignment'.
Recall the primary purpose of random assignment in an experiment. Its main function is to create groups that are equivalent at the beginning of the study.
Next, define each of the options provided. What is the history threat? Maturation? Selection bias? Testing effect?
Compare the purpose of random assignment (creating equivalent groups) with the definition of each threat. Random assignment directly prevents systematic differences between groups, which is the definition of selection bias.

Concept Tested & Keywords

Concept Tested: Threats to Internal Validity in Experimental Research
Stem keywords: threats to internal validity, random assignment, experimental studies
Lead-in keywords: best controlled by
Negative lead-in flag: false

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