Answer:
Number of trials are 250.
Step-by-step explanation:
A researcher finds 15% of all commuters in a metropolitan area take the train to work.
The researcher polls 250 people in the area to ask them whether they take the train to work or not.
We have tell the number of trials for this binomial experiment.
Researcher will do 250 trials to confirm whether they take the train work and this irrespective of their response.
