Question

The manufacturer wishes to set up a control chart at the final inspection station for a gas water heater. defects in workmanship and visual quality features are checked in this inspection. for the past 22 working days, 176 water heaters were inspected and a total of 924 nonconformities reported. a. what type of control chart would you recommend here, and how would you use it?

O the inspections were done one at a time, and no unit is given, so the c chart is not an option.
O we are given a number of nonconformities, not a number of good or bad parts.
O we will use the u chart to create control limits and with each new sample of 22 days being treated as one sample and ensure that the number of nonconformities is not out of control.

Answer 1

A u chart is recommended for the manufacturer's quality control because it tracks nonconformities per unit, and maintains regular oversight to ensure consistent quality. By using the u chart, the process can be monitored and adjusted as needed over time.

Step-by-step explanation:

In the case of the gas water heater manufacturer, the appropriate control chart to use is a u chart. This chart is ideal because it tracks the number of nonconformities per unit, which in this case, are various defects found across multiple units. The manufacturer has observed 924 nonconformities over 22 days for 176 water heaters inspected.

To construct the u chart, the total number of nonconformities (924) is divided by the total number of units inspected (176) to determine the average number of nonconformities per unit. Control limits are then set to monitor whether the process remains in control in the future. For every new sample of 22 days, the number of nonconformities will be compared to these limits to ensure the process has not deviated into an 'out of control' state.

The use of a u chart allows a company to maintain consistent quality control and promptly address any variations in the process, thereby ensuring the final product meets the requisite standards.