Very few U.S. citizens have had trouble swallowing taxation

Samuel is a part of the state police force created during the governorship of Edmund Davis. Which of the following most likely describes one of Samuel's duties?

a. ensuring the protection of African Americans in the Confederacy b. the protection of Texas borders from Indian incursion c. the enforcement of law and order in the state of Coahuila y Tejas d. the protection of the governor from political takeovers

Threats to internal validity from regression to the mean in randomized, posttest-only, control-group designs are controlled by

A) nonrandom assignment of participants. B) random assignment of participants to groups. C) controlling for experimental effect. D) Both A and C