Exam 16: Quality Control and SPC

An operator wants to determine the standard deviation for a machine she operates. To do this, she wants to create a p-chart. Over a month's time, she collects 30 samples of 75 observations each and records the number of errors. The average proportion defective is found to be 0.024. Which of the following is the standard deviation ( ) of the machine?

The time taken for guests to check out at a hotel front desk was measured over the course of several weeks. The management believes that the target time for checking out guests should be between 2 and 3 minutes with a target of 2.5 minutes. The data gathered for the actual process had a mean time of 2.75 minutes with a standard deviation of 0.45 minutes. The process capability index will be:

The task of__________is to ensure that a good or service conforms to specifications and meets customer requirements by monitoring and measuring processes and making any necessary adjustments to maintain a specified level of performance.

If a process has a process capability index value (C p) of less than 1, it means that:

In-process control is typically performed by people who run the back-end processes.

In the context of designing control charts, which of the following is true of a sample size

Keeping special cause variation from occurring is the essence of statistical quality control.

A cell phone manufacturer has been experiencing physical quality control problems. The back case of phones does not always fit and snap into place on the phone body. The dimensions of the case have constantly been in statistical process control (SPC). To monitor process control, the company uses -charts. Seven samples, each containing three phone cases, were selected from different batches. The data is presented in Table 1 below. Table 1: Cell Phone Plastic Case Widths in Centimeters Data* Observation Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 Sample 6 Sample 7 1 6.02 5.92 5.88 5.99 6.05 5.94 6.00 2 5.97 5.83 5.97 6.08 6.06 5.96 5.95 3 5.90 5.87 5.88 6.08 5.98 5.99 5.82 Average 5.963 5.873 5.912 6.051 6.035 5.963 5.923 Range 0.12 0.09 0.09 0.09 0.08 0.05 0.18 *The sample averages and ranges help avoid simple math errors and quicken the time to complete the SPC analysis. If for the -chart is 1.023, the lower control limit for the -chart (LCL) will be:

A detergent company periodically tests its products for variations in the fill weight. To do this, the company uses -charts. Eight samples, each containing six detergent boxes, were selected from different batches. Historical data for fill weight (in ounces) of the eight samples is presented below. Sample Sample Mean Sample Range 1 15.80 0.42 2 16.10 0.38 3 16.02 0.08 4 15.95 0.15 5 16.12 0.42 6 16.18 0.23 7 15.87 0.36 8 16.20 0.40 If A2>for the -chart is 0.483, the upper control limit for the -chart (UCL) will be:

In the context of the net promoter score (NPS), scores of 7 or 8 are associated with__________, customers who are satisfied but may switch to competitors.

Customer waiting time and order lead time are examples of__________.

The value of the process capability index, (Cp), depends on the mean of the process.

Which of the following is true of common cause variation

Jim, a quality control manager at an apparel manufacturing company, studies and monitors quality using R-charts. He discovers a quality problem with the construction of zippers. Jim proposes that 25 samples of eight observations each be collected on a daily basis. He plans to prepare an R-chart to monitor the variation in the size of the zippers. The data collected shows that the mean length of the zippers is 15 inches and the average range is 0.5 inches. If D 3 for the R-chart is 0.136, the lower control limit (LCL R) for the R-chart will be:

Which of the following is true of control charts

The relationship between the natural variation and specifications is quantified by a measure known as the _____.

The 1:10:100 Rule states that if a defect is first detected during the production process, it might cost $1 to fix.

A bottling machine fills water bottles with an average of 12.000 ounces of water. The standard deviation is 0.002 ounces. If the design specification for the fill weight of the bottles is 12.000 ounces plus or minus 0.015 ounces, calculate the process capability index of the machine.

Which of the following is the upper control limit for a c-chart (UCL c) with the average number of nonconformances per unit equal to 7?

Which of the following is true of special cause variation