In a study undertaken at the University of Johannesburg on people suffering from a condition called Moriti wa letswele, it was found that in the 11–20-year group there were seven participants, in the...

In a study undertaken at the University of Johannesburg on people suffering from a condition called Moriti wa letswele, it was found that in the 11–20-year group there were seven participants, in the 21–30-year group there were 15 participants, in the 31–40- year group there were nine participants, and in the 41–50-year group there were five participants. What was the typical age of participants in this study?