Exam 21: Statistical Process Control

A malfunction in the process goes unnoticed and later causes great expense in terms of operator and machine downtime.What type of error was caused here and how could it be decreased?

If your control chart found a series of points all lying within 3 standard errors above the center line,and none lying below the centerline,this could be an indication of assignable variation due to a(n)____________________.

If the control limits of an chart are set at ±2 standard errors from the centerline instead of the commonly used ±3 standard errors,this will result in

The mean of the sample means and the pooled standard deviation of 25 samples of size 4 taken from a production process under control are found to be 150 and 10,respectively.The centerline for the chart is:

Control charts used to determine if the process distribution standard deviation has changed are:

20 samples of size 1,500 were drawn from a manufacturing process and the number of defectives in each sample was counted.The mean sample proportion was .020.The upper control limit for the p chart is:

50 samples of size 2,000 were taken from a production process that is under control.The mean of the sample proportions of defectives was .041.Calculate the centerline and control limits for the p chart.

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 ____________________.

25 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 ,and S = 3.5,respectively.The sample means are listed below. ​ ​ -{25 Samples Production Narrative} Find the centerline and control limits for the chart.

To construct a p chart,draw samples of size n,and for each sample calculate the sample ____________________ of defective units.

We construct a p chart to track the proportion of ____________________ units in a series of samples.

Which of the following is an example of assignable variation in a process?

A process capability index (C_p)of 2.0 describes a production process where the specification limits are equal to 3 standard errors above and below the centerline.

The p chart is an example of control charts for attributes.

If the lower control limit of a p chart is negative,set it equal to ____________________.

The key to quality is to detect when the process goes out of control.The ____________________ chart is the statistical method that we use to detect problems.

If your control chart found a series of points all lying within 3 standard errors above the center line,and none lying below the centerline,this could be an indication of assignable variation due to a(n)____________________.

The mean of the sample means and the pooled standard deviation of 36 samples of size 9 taken from a production process under control are ,and S = 6,respectively.The lower control limit of the 3-sigma chart is 147.

Assume a process has limits set at ±3 standard errors from the centerline.The average run length (ARL)is 385.What does this mean?

In statistical process control,a Type I error occurs if we conclude that the process is not in control when it actually is and requires that production is temporarily stopped.