Final answer:
An r-chart is used for monitoring the variability within control charts, specifically among the options provided. Control charts are a tool in statistical process control to evaluate if a process is under control, and an r-chart looks at the range of variability.
Step-by-step explanation:
An r-chart, also known as a range control chart, is used within the scope of statistical process control to monitor the variability of a process. Among the options provided, an r-chart is utilized for option 1, Control charts. Control charts are used to determine whether a manufacturing or business process is in a state of control. An r-chart specifically helps in monitoring the range of the variability of the process rather than the process capability or the process performance itself.
Other charts and graphs mentioned, such as Histograms, Pareto charts, and Scatter plots, serve different purposes. A Histogram is used to depict the distribution of continuous data, a Pareto chart to highlight the most significant factors in a dataset, and a Scatter plot to investigate the relationship between two quantitative variables.