Me thinks you need to increase your sample size and it's diversity. So head out to the local Mickey D's and get more data
Now here I am in a completely different location with a very different demographic, and my data findings are still valid.
A gang banger punk looking kid with profanity on his t-shirt is more likely to hold the door for a woman than a well-dressed white professional male. Black women still do not say thank you, and neither do white trash women.
Black men in general are more likely to hold the door than their white counterparts, and blue collar men hold the door almost always, regardless of ethnicity. The exception is loud buffoonish moron white blue collars.
Two groups of men: a pack of black ruffians, being loud and catcalling each other, probably using inappropriate language; and a pack of white ruffians the same. You can bet that the black guys will hold the door for you while the white guys will practically trample you to get in the door first.
This is my observation from frequenting the Sheetz on a daily basis, the post office regularly, and assorted other errand locations.