Wk 14- Statistical Process Control

precision

a measure of how close a series of measurements are to one another

precision example

all the darts are close but not in the center

accuracy

how close a measurement is to the true value

accuracy example

darts all over the place but on the target

what does a process that has low variability also have

accuracy and precision

accuracy and precision example

all the darts are on the bullseye

normal distribution properties

can be described completely by knowing only the mean and standard deviation, the area under sections of the curve can be used to estimate the cumulative probability of a certain event happening

68% of all values are within ______ SD

1

95% of all values are within _____ SD

2

99.73% of all values are within _____ SD

3

assignable variation

deviation in the output of a process that can be clearly identified and managed

common variation

deviation in the output of a process that is random and inherent in the process itself

upper and lower specificiation limits

the range of values in a measure associated with a process that is allowable given the intended use of the product or service

bassic assumption of process quality control

every process has random variation in it, production processes are not usually found in a state of control

the state is in control if the process is

stable and predictable