Given:
Number of people = 50000
Sample size = 150
Given that the researchers want to start the study immediately and do not need a representative sample, the appropriate sampling method to use in this scenario is the convenience sampling method.
Convenience sampling can be said to be a type of sampling method where a researcher draws samples from the population that is close to hand or easier to reach.
In convenience sampling, the participants are selected based on willingness to take part or based on availability.
In this case, since the researchers want to start the study immediately and do not need a representative, it means they are likely to collect the sample from the population that is easier to reach.
Therefore, the appropriate sampling method for this given scenario is the convenience sampling method.
ANSWER:
Convenience.