The method most likely to produce the most precise line of cost behavior and require the least amount of judgment is the scatter diagram.

The method most likely to produce the most precise line of cost behavior and require the least amount of judgment is regression analysis, not the scatter diagram. The scatter diagram is a useful tool for visualizing the relationship between two variables, but it does not provide a precise line of cost behavior. Regression analysis uses statistical techniques to estimate the relationship between two variables and can provide a more precise line of cost behavior.