Chapter 6 Flashcards
is caused by factors that can be identified and managed
Assignable variation
testing a sample of output to determine if the process is producing within a preselected range
Statistical Process Control
Sampling to accept or reject the incoming material or outgoing finished goods.
Acceptance Sampling
a methodology for monitoring quality of manufacturing and service delivery processes to help identify and eliminate unwanted causes of variation
Statistical Process Control (SPC):
The essence of statistical process control is to assure that the output of a process is ____ so that future output will be ____(common variation)
Random
concerned with monitoring quality while the product or service is being produced
Process control:
run charts with control limits added to monitor process output to see if it is random
Control charts:
chosen statistically to provide a high probability that points will fall between these limits if the process is in control
Control limits
a system governed only by common causes
stable system
if no special causes affect the output of the process
in control
when special causes are present in the process
Out of control:
variation that is inherent in the process itself
Common (or natural) variation:
one that is calculated from data that are MEASURED as the degree of conformance to a specification on a continuous scale of measurement
Continuous metric (variable data)
one that is calculated from data that are COUNTED
Discrete metric (attribute data)
a plot of the means of the samples taken from a process
Used to monitor the central tendency (mean) of a process
X-bar charts:
a plot of the range within each sample
The range is the difference between the highest and lowest numbers in each sample
Used to monitor the process dispersion
R-chart:
: Control chart used to monitor the percent (or proportion) of defectives in a process
When observations can be placed into two categories
Examples: good or bad, pass or fail, operate or don’t operate
p-Chart
Control chart used to monitor the number of defects per unit
Used when not possible to compute population percentages
Use only when the number of occurrences per unit of measure can be counted; non-occurrences cannot be counted
c-Chart:
constructed from historical data, the purpose of a ___ is to help distinguish between natural variations and variations due to assignable causes
control charts
Range of acceptable values established by engineering design or customer requirements
Specification (or tolerance) limits:
the determination of whether the variability inherent in the output of a process that is in control falls within the acceptable range of variability allowed by the design specifications
Process Capability (Cp):
