Your thesis cannot be a question. It must be a statement.
Not: Do manners matter?
But: Manners matter.
Collect evidence from your source.
What is evidence?
facts, examples, statistics, etc. that support a claim
What could you prove?
Is your thesis broad enough?
We need manners to help Americans be safer.
(It is only broad enough if all of your evidence is about how manners make Americans safer and why we need to be safer.)
Is our thesis too broad?
Everyone should be nice.
Be careful how you use statistics and the results of surveys and studies as a hook or as evidence in the body of the essay.
Survey Result quoted in the Scope article:
"Sixty-nine percent of American adults surveyed in 2010 said they think Americans are getting ruder."
Based on that evidence, could you say this?
"69 percent of people say that manners matter."
or
"Do you like it when someone is rude to you? Well, neither does 69% of adults in America."
Which of these could serve as thesis sentences for an argument essay?
1. Do manners matter?
2. Manners
3. Over half of American adults surveyed said they think Americans are becoming ruder.
4. Good manners could make our society safer, more successful, and happier.
