A retail psychologist investigates whether background music tempo influences the walking speed of shoppers. On alternating days over two weeks, they play either fast-tempo or slow-tempo instrumental music in a large department store and record the time it takes customers to walk down a designated aisle.
Which of the following is a methodological weakness of this research design?
The highly artificial setting and task increase the risk of demand characteristics.
The researcher is unable to manipulate the independent variable, preventing a cause-and-effect relationship from being established.
Extraneous environmental variables are difficult to control, which may threaten internal validity.
Random allocation of participants is mandatory, which increases the likelihood of selection bias.
