Case 7 Quality Associates

1377 Words6 Pages
Quality Associates, Inc. is a consulting firm who advises its clients about statistical and sampling methods that can be used to control their manufacturing procedures. In this particular case we consider a production line designed to fill bottles of a shampoo with a mean weight of 12 ounces of shampoo per bottle. Quality Associates, Inc. made a quality control testing of the manufacturing machine of this client (Alibaba Machinery), to determine if the process is operating properly or if, perhaps, a machine malfunction has caused the process to begin underfilling or overfilling the bottles. The client picked a sample of 800 bottles taken during a time when the machine was
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and 12.10fl.oz.

The quality control inspection in this case study does not consider the quality of the shampoo which is being poured into the bottles; this is assumed to be constant. Moreover, the quality of the bottle (i.e. no defect) and proper labeling are not considered in this study, but also assumed to be constant.
Another limitation may be the systematic sampling method used to collect each sample. One of the conditions that should be satisfied when a random sample is selected from an infinite population is that each element selected comes from the same population. To ensure that this condition is satisfied, the bottles must be selected at approximately the same point in time (p. 270). This is so that the inspector avoids the possibility of selecting some bottles when the machine is operating properly, and other bottles when the machine is not operating properly and is underfilling or overfilling the bottles. In the methodology assumed to be used for this case study, the 30 bottles selected for each sample are selected within a period of one hour.

Analysis & Interpretation of table & graphs in relation to solving the issue raised at the start.

Box plots (p. 112): (i) Sample 4 has the highest bottle weights. The lowest bottle weights are in Sample 3. (ii) Sample 4 has the highest median weight, followed by Sample 2, and then Samples

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