Exam 21: Statistical Process Control

Control limits for the p chart are typically placed so that they are 3 standard errors above and below the centerline.

Describe the three essential parts of a control chart.

A trend indicates there is a slow and steady shift in the ____________________ of a process distribution.

Samples Production 25 samples of size 4 were taken from a manufacturing process.The mean of the sample means and the pooled standard deviation are $\bar{\bar { x }} = 13.9$ ,and S = 3.5,respectively.The sample means are listed below. -{25 Samples Production Narrative} Is the process under control? Discuss.

When the $\bar { x }$ control chart shows a change in the mean of the process distribution,the result is referred to as:

The ____________________ is the expected number of samples that must be taken on average,before the control chart indicates that the process has gone out of control.

Suppose previously your company decided that a process is out of control when the mean shifts by about 1 standard deviation.Now your company wants to declare a process as being out of control when the mean shifts by .50 standard deviations.In order to do this,the samples must be collected ____________________ often and/or the sample sizes must be ____________________.

Diaper Delivery Wrap-M-Up,a Ft.Lauderdale diaper Service,has 10 delivery men who each deliver diapers to 50 customers every day.Wrap-M-Up decides to record the proportion of diapers delivered on time for a 10-day period and construct a p chart to see whether the proportion is too erratic.The data are shown below: Day 1 2 3 4 5 6 7 8 9 10 Prapartion of Dingers .916 .894 .928 .900 .864 .968 .914 .988 .952 .936 Delivered an Time -In order to ensure that a manufacturing process is under control,50 samples of size 1,000 were drawn and the number of defectives in each sample was counted.The mean sample proportion was .0234.Compute the centerline and control limits for the p chart.

Which of the following is NOT something you can do with an operating characteristic curve?

Samples Production The mean of the sample means and the pooled standard deviation of 40 samples of size 8 taken from a production process under control are $\bar{\bar { x } }= 215.6$ ,and S = 14.5,respectively. -{40 Samples Production Narrative} Compute the zone boundaries for the $\bar { x }$ chart.

If a p control chart finds six increasing or six decreasing sample proportions in a row,this could be an example of assignable cause variation called a(n)____________________.

When the $\bar { x }$ control chart shows an increase in the standard deviation of the process,the result is referred to as:

The average run length indicates how often a false alarm is expected to occur.That is,the average run length is one divided by the probability of a Type ____________________ error.