Researchers randomly divide participants into groups. each group takes a different amount of omega-3 fatty acid supplements daily for a month. one group receives a placebo. the researchers measure the impact on cholesterol levels in the blood. what is the purpose of random assignment in this experiment? check all that apply. to ensure that all people with high cholesterol have an equal chance of being selected for the study to increase the accuracy of the research results and prevent skewness in the data to produce treatment groups with similar characteristics to control confounding