Which native american tribe is most noted for converting to christianity, publishing its own newspaper, and owning slaves?

there is an explationation of this on a site called crash   course world history 1

this null effect is caused by a weak manipulation and ineffective internal validity. in a scientific study, as the one dr. morimoto is trying to perfom, internal validity refers to the confidence placed in the cause-effect relationship and to how well an experiment is done and able to eliminate confounding variables.