Final answer:
In an experiment to test if watching television increases aggressiveness among children, the independent variable is the amount of violent television content watched. The dependent variable is the level of aggressiveness observed. Research indicates a potential causal link but also suggests considering other contributing factors.
Step-by-step explanation:
A researcher interested in testing the proposition that watching a lot of television causes increased aggressiveness among children at school can conduct an experiment where the independent variable is the amount of television watched, particularly the exposure to violent content. The dependent variable could be the levels of aggressiveness observed among the children in school settings.
To accurately measure the impact, participants would be randomly assigned to two groups: one that watches violent television programs and another that watches nonviolent content. Through careful observation and data collection, comparisons would be made to see if there is a significant difference in aggressive behavior between the two groups, which would suggest a causational link.
Research summarized by Anderson and Bushman indicates that there is evidence of such a causal relationship between exposure to violent media and aggressive thoughts and behaviors. This debate in psychology is ongoing, with other factors such as mental health and family life also considered in more recent studies by researchers like Ferguson.
Ultimately, the findings from such an experiment must be meticulously documented and can be reported in scholarly journals following guidelines such as those set by the American Psychological Association (APA).