Nearly Half of Detroit's Citizens Are Illiterate?

The National Institute For Illiteracy recently reported that 47% of the ADULTS in the city of Detroit is illiterate....47%
That's what the report says and since the report says it, it must be true, right?
Let me ask you something:
Have you ever noticed that certain people and certain organizations poll a select group of people to get the desired result they want?

Example: FOX "news" is STILL reporting that almost 38% of "Americans" believe President Obama wasn't born in this country.
Do you think they poll anyone who doesn't watch their propaganda news network? OR, do you think they poll the people who view their website and other outlets that drive home the "birther" issue?
 Probably the latter, which is why the people of Detroit should be marching in the streets, protesting this report.
I refuse to believe that almost half of a city's ADULT population can't read or write.
I mean sure, last year their school Superintendent admitted he was illiterate, but I'm sure he just slipped through the cracks-right?
Let's start calling on the people who conduct these reports to publicly show the areas they studied and show the criteria they based their final decision on. Because a charge THIS serious is grounds for a lawsuit. That is, IF the report is false.