The upper and lower limits for diving ring diameters made by John's Swimming Co. are 40 and 39 cm., respectively. John took 11 samples with the following average diameters (39, 39.1, 39.2, 39.3, 39.4, 39.5 39.6, 39.7, 39.8, 39.9, 40). Is the process in control?

Statistical process control (SPC) is a data-driven process that uses statistical methods to monitor and control the quality of a production process. The goal of SPC is to ensure that the process is stable, consistent with customer requirements, and not drifting or changing in an unexplainable manner. 

SPC is commonly used in manufacturing or production processes to measure how consistently a product performs according to its design specifications. Some of th