The Fred and Barney Cookie Co. has been baking chocolate chip cookies for many years, yet is just now looking to implement statistical process control. Managers are particularly concerned about the number of burned or broken cookies coming out of the baking process and heading into the packaging process. Traditionally, they have sampled the finished product but obviously it is better not to package burned or broken cookies at all. To get SPC up and running, they have decided to track burned cookies. Four times per day over the last five days, they have taken 20 samples of 1,000 cookies each as they came out of the oven and counted the burned cookies in each sample. Use the chart below to answer these questions:
Are the managers dealing with a variable or an attribute?
What type of control chart should they use?
What are the upper and lower control limits of their control chart? Show your answers with four decimal places.
Is the process in control now? How do you know?