Answer:
Field Experiment.
Explanation:
A Field experiment is defined as the kind of experiment that is conducted in a real-life setting.
Lily is conducting a 'field experiment' as she conducts the experiment in the natural setting('two groups of trials for counting the number of people lining up early to board an airplane at the airport'). Such an experiment will allow her in producing more authentic and reliable outcomes as there is very little interference or control over the variables.
