Final answer:
The best research method for the hypothesis concerning children under five exhibiting aggressive behavior in large groups is observation, ideally within an early education setting. This method allows for direct and systematic monitoring of behavior without the need for self-reported data by the children themselves.
Step-by-step explanation:
To determine which research methods would best suit the hypothesis that children under the age of five are more likely to exhibit aggressive behavior when placed in groups of ten or more, one should consider the nature of the behavior being studied. Surveys and interviews typically gather self-reported data, and while useful, might not be the best methods for studying behavior in young children. Statistical analysis is a tool that can be applied to data once it's collected but is not a method of data collection in itself. Therefore, the most appropriate research method would be observation, ideally in a controlled or natural setting, which allows for the direct monitoring of children's behavior in groups.
In a controlled experiment, the researcher could manipulate group size and directly observe the behavior of children. In observational studies, researchers systematically watch and record behavior as it naturally occurs, without intervention. Considering the difficulties of making a researcher's presence invisible (e.g., in kindergartens or specific social situations), direct observation is the most practical and ethical approach to studying children's behavior in this context. For the specific hypothesis about children's behavior in large groups, an observational study within an early education setting would provide the richest data.