Choice "C" is correct. A Pareto diagram represents an individual and cumulative graphical analysis of errors by type. Individual error types are represented on a histogram (bar graph) while the cumulative number of errors is presented on a line graph. The Pareto diagram is used to prioritize process improvement efforts.
Choice "a" is incorrect. A control chart shows the performance of a particular process in relation to acceptable upper and lower limits of deviation. Performance within the limits is termed statistical control. Processes are designed to ensure that performance consistently falls within the acceptable range of error.
Choice "b" is incorrect. A fishbone diagram describes a process, the contributions to the process and the potential problems that could occur at each phase of a process. The chronological sequence of events is represented by a single horizontal line while the contributions to the process are represented by diagonal lines that create the image of a fishbone.
Choice "d" is incorrect. A value chain analysis is a macro level flowchart that shows the relationship between broad functional areas, the product delivered by the organization and manner in which value is added at each link in the chain.