What method is applied for understanding the beliefs and feelings consumers have about products?

The method that is instrumental in understanding the beliefs and feelings consumers have about products is diagnostic analysis. This approach focuses on exploring and uncovering insights into consumer attitudes and perceptions, allowing marketers to delve deeper into the reasons behind consumer behavior. By identifying the underlying factors that influence how consumers feel about a product, diagnostic analysis helps businesses to address issues and tailor their marketing strategies effectively.

In contrast, descriptive analysis primarily summarizes past data and trends without providing the deeper insights needed to understand consumer feelings. Predictive analysis is concerned with forecasting future trends and behaviors based on existing data rather than examining current sentiments. Market segmentation is about dividing consumers into distinct groups based on characteristics and behaviors, but it doesn't specifically analyze their beliefs and feelings about products. Thus, diagnostic analysis stands out as the correct method for gaining nuanced insights into consumer perceptions.