Why if a control group is not included in an experiment is difficult to draw a valid conclusion

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? a, to produce treatment groups with similar characteristics b, to ensure that all people with high cholesterol have an equal chance of being selected for the study c, to increase the accuracy of the research results and prevent skewness in the data

Models are non-visual ways of coummincating how someone thinks about something in the natural world

Which example would the nurse consider to be a part of systems thinking theory?