Chained dogs are 3 times more likely to bite than unchained dogs.

Really??? I doubt this...

Never mind! I did my resaerch, this is true.

I'd have to say DUH, there's a reason they're on a chain

The owner isn't doing a very good job at holding it back then...

What Amy is saying has some logic to it, but this is not what the fact is trying to say.
What this says is that chained dogs are more likely to bite because they get treated differently and are stressed with no freedom.