Individual operations management report

Lately, the company has been facing tough competition from Chinese manufacturers impacting both its top line and bottom line. In order to improve the situation, the company has initiated a quality improvement plan. Statistical Process Control is being used at one of its toy plants as one of the tools for enabling Total Quality Management.
Under this initiative the company plans to analyze the quality of a doll manufacturing unit due to growing concerns over increasing customer returns. The company has decided to evaluate two important parameters of quality – colouring and height of the dolls. The data has been collected over a 30 day period.
Statistical Control charts are of various types and are used depending upon the situation and the nature of data recorded. For the first set of data, that is, the data for colour defects, c-chart would be the most appropriate control chart since c-chart is used for the number of defects. Since, the number of units tested is constant (=200) in each sample, c-chart is perfect for the situation. Else, a p-chart could have been used.
The values of constants A2, D3 and D4 are taken from standard tables for control chart constants (Here values for n=25 have been assumed for the sample size of 30 as the tables contain values till n=25 and calculating annually for higher values is very cumbersome) (Table for Control Chart Constants).
For the colour defects, only 1 value (14) is found to lie outside the two control limits. Hence, from the colour defects point of view, the process is only marginally out of control. The control chart for the same is shown in Figure 1.
For the heights, a large number of values in both R chart and x bar chart are found lie outside the control limits. Thus, this is a major concern area for the company. The two control charts for the same are shown in the Figures 2 and 3.
Tom Pulling Toys needs to pay some attention to