Trial types refer to the different methods used in research to test hypotheses and evaluate the effectiveness of interventions. Common types include randomized controlled trials (RCTs), where participants are randomly assigned to different groups, and observational studies, which observe outcomes without intervention. Each type has its strengths and weaknesses, influencing the reliability of results. Another important trial type is clinical trials, specifically designed to assess new medical treatments or drugs. These trials often progress through phases, starting with small groups to test safety and moving to larger populations to evaluate efficacy. Understanding these trial types helps in interpreting research findings accurately.