A researcher pretests a group of participants to determine their attitudes toward the use of alternative energy sources to replace crude oil. The researcher then initiates a program to convince them that they should invest in such alternatives. During this time, the price of gasoline rises $.50 per gallon. At the end of the program, the researcher retests and finds that the participants are much more positive in their attitudes. What threat to internal validity most likely accounts for this change?

Policies that physically separate a minority group from the dominant group.

During the 1500s,most rulers supported established a. political systems. d. none of the above b. churches c. freedom of speech

Ascientist successfully predicts the outcome of an experiment. you watch carefully and know he didn't cheat. the scientist's success shows that: a) the scientist knows absolute truth about this experiment; success is not possible unless you know the truthb) the scientist was just lucky; no one ever knows what's going on, so successful predictions require luckc) the scientist may know the truth, or at least know something that is close to the truth, or the scientist may have gotten lucky this time; you can't be absolutely sured) the scientist really was cheating, even though you didn't see the cheating; no one can get things right, except by cheatinge) the scientist spent the night at a particular hotel chain and go a free breakfast, giving the scientist the ability to do amazing things