The correct answer is 60 participants in total.
If Pattie observes 15 participants in each of the four groups, you'd calculate
the total number of participants by multiplying the number of participants in
each group by the number of groups.
So, Pattie observes 15 participants in each of 4 groups:
15 participants/group * 4 groups = 60 participants
Therefore, the correct answer is 60 participants in total.