Control Charts Research Paper Example | Topics and Well Written Essays - 500 words

Control Charts - Research Paper Example The items that are being considered may have one or more quality characteristics that should be inspected at the same time. The item is considered non –conforming or flawed if one of the characteristics under assessment does not match or correspond the laid down standards. The proportional charts can be said to track the proportion of defects and are used when evaluating a product with regard to a certain standard and hence classifying it as being defective or otherwise. These charts plot the proportion of defective items per subgroup. The data collected are the number of flawed items and is assumed to follow a binomial distribution with an unidentified proportional parameter P. The C chart is applicable when a product is known to have various defects, which are controllable. C charts track the number of flaws per unit sampled. C charts are usually used when dealing with an intricate product or service. The C chart requires the following assumptions in order be effectively utilized: it assumes that the likelihood of non-conformity is small at any given location; secondly, the C charts assume that the probable locations for conformity are very huge. The C charts plot the number of defects per unit and the data composed is the total number of defects in every subgroup, which is known to follow poisons distribution with an unknown mean number of defects in each subgroup. Control limits for control charts are basically in the control phase of a six sigma project. These charts should be sensitive enough be able to quickly give a signal when a special cause exists. Assessment of sensitivity is achieved by calculating the number of subgroups needed to signal a special cause. Good control charts should never give a false alarm when the process is controllable.