An educational psychologist plans to conduct an experiment using a repeated measures design to investigate whether the presence of an environmental scent (lavender vs rosemary) affects performance on a rapid-fire mental arithmetic task.
Which of the following procedures is the primary method used to control for order effects (such as practice or boredom) in this study?
Using a double-blind technique where neither the participants nor the research assistant knows which scent is being administered in each trial
Implementing counterbalancing, where half of the participants perform the task with lavender first and then rosemary, while the other half complete the rosemary condition first
Randomly allocating participants to either a lavender-only group or a rosemary-only group using a computer randomiser
Pre-testing participants on arithmetic ability and pairing them based on similar scores before assigning them to different groups
