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Block Randomization
Block randomization is a modified random assignment strategy used to keep sample sizes similar across groups. A sequence is created where every condition appears once in a randomized order within a designated block before any condition is repeated. As each new participant enters the study, they are assigned to the next available condition in this pre-generated sequence.
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Research Methods in Psychology - 4th American Edition @ KPU
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Role of Random Assignment in Ensuring Group Comparability
A researcher wants to test if a new type of energy drink improves performance on a memory test. After recruiting 100 volunteers, which of the following procedures is the most effective way to create an experimental group (receives the energy drink) and a control group (receives a placebo)?
Block Randomization
Fallibility of Random Assignment
Random Assignment vs. Random Sampling
Modified Random Assignment
Software for Randomization
Using a Random Number Generator to Understand Randomization
Example of Simple Random Assignment
What is the primary function of random assignment in an experimental design?
A researcher assigns the first 30 participants who arrive at the lab to the treatment group and the next 30 participants to the control group. This method successfully achieves random assignment because both groups have an equal number of participants.
Match each core requirement or outcome of random assignment with the description that best explains its role in ensuring a fair experiment.
Ensuring Randomness and Statistical Power in Randomized Controlled Trials
In a between-subjects experiment, random assignment is the primary tool for establishing internal validity. Sequence the following steps to represent the logical progression from the initial procedural action to the final scientific conclusion.
A research team is designing an automated system for a study where they will compare three groups: Condition A, Condition B, and Condition C. To construct a protocol that strictly satisfies the definition of random assignment, which logic should the team program into their system?
Strictly speaking, random assignment requires that every participant has an equal probability of being placed in any condition and that each individual's assignment is completely independent of the others.
To effectively control for extraneous variables, researchers must follow a specific procedural logic. Arrange the following steps to correctly sequence the process of random assignment for participants in an experiment.
A researcher evaluates an experimental protocol where participants who arrive at the lab in pairs are always assigned to the same condition to ensure they remain together. Methodologically, this protocol is flawed because it fails to satisfy the strict definition of random assignment, which requires that every individual's placement must be completely _____ of the others.
Match each component or requirement of random assignment with its correct description based on the strict methodological definition.
A researcher evaluates an experimental protocol where participants who arrive together are always placed in the same group. This protocol violates the strict definition of random assignment because each participant's assignment is not _____ of the others.
Block Randomization
What is the primary purpose of using a modified random assignment procedure instead of strict random assignment?
If an experiment using strict random assignment ends up with unequal group sizes, a researcher should discard some data from the larger group to equalize them and improve statistical efficiency.
A researcher wants to assign 10 participants to two conditions—'Social Interaction' and 'Isolation'—using a modified random assignment approach to ensure exactly 5 people are in each group. Arrange the following steps in the correct order to implement this procedure.
Analyze the logic of participant assignment in experimental design. Match each methodological concept with the corresponding procedural outcome or logical justification as described in the context of random assignment.
According to the course text, having unequal sample sizes in different experimental conditions is generally not a significant issue.
A researcher uses a simple coin-flip procedure for a study with participants and ends up with people in the treatment group and in the control group. How would the use of a modified random assignment approach have changed this outcome?
When evaluating whether a strict random assignment procedure produced unequal groups of and participants, a researcher should recognize that these groups are less statistically _____ than equal groups of and , yet must retain data from all participants.
Match the following experimental scenarios to their appropriate methodological action or description based on random assignment principles.
An investigator analyses their study design and notes that while unequal group sizes from coin-flipping are not a serious issue, having equal-sized groups for a fixed number of participants is statistically more _____.
A research team evaluates their participant assignment procedures after completing a study. Arrange the steps of their methodological evaluation and decision-making process in the correct logical order.
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Block Randomization Sequence Example
A researcher is conducting a study with three experimental conditions: 'High Stress,' 'Low Stress,' and 'Control.' To ensure that the number of participants in each condition stays balanced even if the study ends early, the researcher uses block randomization. Which of the following best explains how this process is implemented?
A researcher is conducting a study with two conditions: 'Visual' and 'Auditory'. They decide to use block randomization to ensure balanced group sizes. Arrange the following steps in the correct order to assign the first four participants using this method.
A researcher uses block randomization to assign participants to two conditions ( and ). Following the rule that every condition must appear once within a block before any condition is repeated, the assignment sequence is valid, while the sequence is invalid.
A researcher must evaluate the methodological advantages of block randomization across different experimental designs. Match each research scenario with the specific evaluative rationale for why block randomization is considered the superior assignment strategy in that context.
Which of the following best defines 'block randomization' as used in psychological research assignment?
Match each component of the block randomization technique with the description that best explains its functional role in maintaining balanced experimental groups.
_____ randomization is a modified random assignment strategy used to keep sample sizes similar across groups by creating a sequence where every condition appears once in a randomized order within a designated block before any condition is repeated.
A researcher running a three-condition experiment is concerned that unexpected participant dropout could leave her groups severely unbalanced before data collection is complete. She decides to adopt block randomization instead of simple random assignment. Given that block randomization assigns each condition exactly once within every block before any condition repeats, her groups will remain within a small, predictable margin of each other in size even if data collection ends prematurely.
A researcher uses block randomization to assign participants to three conditions (A, B, and C). After enrolling 13 participants, data collection is unexpectedly halted. Because every block in the pre-generated sequence contains each condition exactly once before any condition is repeated, the maximum number of participants by which the largest group can exceed the smallest group at this stopping point is _____.
A research methods consultant must evaluate whether a study team should adopt block randomization for an upcoming experiment. Arrange the following evaluative steps in the correct order.