Question

How can you tell if an author of a nonfiction piece is credible?

if his or her writing appeals to the emotions
if the author uses a lot of statistics to prove his or her point
if the author is considered an expert in his or her field
if the author is well-known and widely read

Answer 1

if the author uses a lot of statistics to prove his or her point

Answer 2

if the author is considered an expert in his or her field