In the USA before the abolition of slavery, it's easy to conceptualize that different slave-owners treated their slaves differently. There might have been sadists who tortured their slaves, and there might have been those who were kind with them and considered them almost family. And probably many between the two extremes who only cared about profit.
However, is there any information about their statistical distribution? Around how much percent were excessively brutal with their slaves, and around how much percent were treating their slaves humanely?
Please, no general opinions or politically motivated rants. I'm only interested in serious sources. The perfect answer would cite surveys or statistics, or if such information is non-existent, then contemporary sources from which an approximation could be reliably inferred.