A developmental psychologist is planning a study to investigate whether a new interactive reading programme increases vocabulary retention in primary school children. To ensure that the psychologist's own expectations do not unconsciously influence how they interact with or score the children during the final vocabulary assessment, which of the following procedures should be implemented?
Utilizing a matched-pairs design based on the children's baseline reading ability.
Standardising the physical environment and temperature where the final assessment takes place.
Employing a double-blind procedure so that the assessor is unaware of which programme each child completed.
Counterbalancing the order in which the reading programmes are completed by each child.
