Having studied students in a sufficiently large number of classes, you might say something like:
The average number of professional athletes per class is 0.15.
On average, there are 0.15 professional athletes per class.
This seems awkward, because there are no fractions of people in a class. Of course the phrase is technically (and I think even semantically) correct, because the average is in essence a fraction.
One way could be to define the quantity first, but this doesn't seem to be possible for all cases (my first example for instance):
Define household size as the number of people living in a household. The average household size in the US is 2.54. 1
Solution for expressing percentages
With percentages (not exactly the same, but a neat example) you could use the following phrases to convey the same meaning (numbers are made up):
60% of people like eating cheese.
3 out of 5 people like eating cheese.
Is there a comparable way to avoid the awkward fraction in the example about averages?
'The examples are perfectly fine, why look for another phrase?'
I agree that the examples are fine, concise and correct. I am asking the question here, on a forum of English language enthusiasts, because (for the sake of this question) I am interested in how to communicate to the general public, including younger people, those who are new to the English language and those who only engage with numbers and statistics sporadically.
An interesting read on communicating science to the general public can be found in this article on Scientific American. This partial quote from the article that sums it up nicely:
”The broader audience science can reach, the bigger the benefit in terms of the new ideas you are transmitting as a scientist.”
The quote is from M. Du Sautoy, who according to the article is the Professor for Public Understanding of Science and a Professor of Mathematics at the University of Oxford.