CONTROL PHASE Flashcards
TYPE of Statistical Process Control for these charts: X-BAR chart X-S chart I-MR Chart P-CHART np-Chart u- chart c- chart
shewhart charts
TYPE of Statistical Process Control for these charts:
EWMA Chart
CUSUM Chart
Control Methods
Time-weighted control charts
determines whether the process variation is consistent or unpredictable
CONTROL CHARTS
T/F
A process is considered in statistical control when only common causes are present
TRUE; process variation is controlled, the process becomes predictable
Misinterpretation can lead to the following:
Under-reacting ( missed prevention) & Tampering (increases variation)
when to use X BAR Charts-
most common, applied to higher volume of data or service; inappropriate for range
when to use R charts
most common; used to plot values of the range to control a variables variability. subgroup size < 8
when to use S charts
most common; used to plot values of standard deviation to control a variables variability subgroup size > 8
When to use I Charts
used to plot individual values to control a variables variability
when to use MR Moving Range
low volume of data, long cycle time to build product or serve customer,
types of charts for continuous data
X BAR, R, S, I, MR
Defective Charts are
P & NP used to plot the % of defectives and complete control limits based on binomial distribution
Defect Charts are
c & u used to plot the number of defects per unit and compute control limits on the basis of Poisson distribution
minitab for I-MR charts
Stat>Control Charts> Variables Charts for individuals> I-M
minitab for P-charts
Stat>Control Charts>Attributes Charts> P
minitab for U-Charts
Stat>Control Charts> Attributes Charts> U
T/F
Time-weighted control charts are more sensitive to detecting small shifts in the shirt-run/low volume process mean than Shewhart Chart
True
what type of control chart should be used first to study process instability?
Shewhart control
OR
Time weighted control charts
Shewhart
Why do we need control plans?
sustainability
predictive information
good control plans
____ actions are usually less successful
_____ actions will last longer
compensating & preventative
P CHARTS
used to plot proportion of defective units
NP CHARTS
used to plot the number of defectives units
C CHARTS
used to plot the number of defects, sample is constant
U CHARTS
used to plot the number of defects per unit; sample is variable
