CIC3640 • SPC and Capabilitylearningmedia0.motorolasolutions.com/services/edu/...Calculate the Capability Indices Step 8. Make recommendations for process improvement. Cautions in

CIC3640 • SPC and Capability

Participant Job Aid

CIC3640, 11/16/07 Version 3-0 MOTOROLA and the Stylized M Logo are registered in

the U.S. Patent & Trademark Office. All other product or service names are the property of their respec-

tive owners. © Motorola, Inc. 2007.

This page intentionally left blank.

©2007 Motorola CIC3640 11/16/07 Ver. 3-0 Page 1

1-2Fundamental Steps for Constructing Control Charts 1) Select the quality characteristic to monitor 2) Ensure that Measurement System is stable and capable 3) Determine the sampling procedure 4) Select the appropriate control chart 5) Collect data and check for standard assumptions (for variable control charts) 6) Analyze and interpret the data

Choose Appropriate Control Chart

VariationSample Standard DeviationS

VariationSample RangeR

MeanSample MeanXbar

VariationMoving RangeMR

MeanIndividual ValuesI

Characteristic MonitoredCharacteristic PlottedChart Type

Variable Control Charts

VariationSample Standard DeviationS

VariationSample RangeR

MeanSample MeanXbar

VariationMoving RangeMR

MeanIndividual ValuesI


Variable Control Charts

Number of defectsNumber defects per unitu

Number of defectsNumber of defects in a samplec

Fraction or percent defective

Fraction defective in a samplep

Number defective unitsNumber of defective units in a samplenp


Attribute Control Charts

Number of defectsNumber defects per unitu

Number of defectsNumber of defects in a samplec

Fraction or percent defective

Fraction defective in a samplep

Number defective unitsNumber of defective units in a samplenp


Attribute Control Charts

Type of data:Variable or Attribute


Testing Independence Assumption Time Series Plot

LED Backlight test.mtw from CIC3640 is used as the example • Menu: Graph ► Time Series Plot… • Select Time Series Plots: Simple • Series: LED Backlight Test (mA)

Runs Test LED Backlight test.mtw from CIC3640 is used as the example

• Menu: Stat ► Nonparametrics ► Run Test… • Variables: LED Backlight Test (mA)


Testing Normality Assumptions Normality

Test LED Backlight test.mtw from CIC3640 is used as the example • Menu: Stat ► Basic Statistics ► Normality Test… • Variable: LED Backlight Test (mA)

Control Charts - Variable I-MR Control Charts

LED Backlight test.mtw from CIC3640 is used as the example • Menu: Stat ► Control Charts ► Variable Charts for Individuals ► I-MR… • Variables: LED Backlight Test (mA)


Xbar-R Control Chart Battery Standbytime.mtw from CIC3640 is used as the example

First, use Minitab to calculate the mean and add this new column to the worksheet. • Menu: Calc ► Row Statistics… • Input variables: 1 – 5 • Columns 1 through 5 are used in the example • A new column is created in the worksheet

Test the mean data points for Independence – Time Series • Menu: Graph ► Time Series Plot… • Series: mean


Test the mean data points for Independence – Runs Test • Menu: Stat ► Nonparametrics ► Runs Test • Variables: mean

Normality Test • Menu: Stat ► Basic Statistics ► Normality Test…

Create Xbar - R Chart • Menu: Stat ► Control Charts ► Variable Charts for Subgroups ► Xbar-R…


Xbar - S Control Chart Battery Standbytime.mtw from CIC3640 is used as the example

First, use Minitab to calculate the mean and add this new column to the worksheet. • The above example (Xbar – R Chart) contains the steps for checking that the plotted points

(Mean) are independent and normal • Menu: Stat ► Control Charts ► Variable Charts for Subgroups ► Xbar-S…

P Control Chart GSM Surf Test.mtw from CIC3640 is used as the example

• Menu: Stat ► Control Charts ► Attribute Charts ► P…

U Chart Wings.mtw from CIC3640 is used as the example • Menu: Stat ► Control Charts ► Attribute Charts ► U…


Capability Study Procedure: Continuous Data

A process capability study generally consists of eight steps: Step 1. Select Quality Characteristics for Capability Study Step 2. Ensure that Measurement System is stable and capable Step 3. Determine Sampling Strategy Step 4. Verify the specifications. Step 5. Verify that the process is stable using right control chart Step 6. Determine if the data distribution is normal. Step 7. Calculate the Capability Indices Step 8. Make recommendations for process improvement.

Cautions in the Use of Capability Indices (Cp, Cpk, Pp, Ppk) • Do not use Cpk without Cp or Ppk without Pp when measuring the capability of a

2-sided specification process. A capability index is only as meaningful as the specifications on which it is based.

• If the specifications are on individual measurements, then don’t use the standard deviation of sample means to compute the indices and vice-versa.

• If the specifications for a process output change, then the capability indices must be recalculated.

Do not compute: • Capability indices for attribute data (e.g. number of defects, particle counts). • Simple averages of capability indices across several processes. • Do not use a small number of runs or measurements to compute indices. • Capability indices on unstable processes. • Capability indices when the distribution is not normal. • Capability indices when the individual data values are not independent.


Step 7: the Capability Indices Antenna Diameter.mtw from CIC3640 is used as the example

• Menu: Stat ► Quality Tools ► Capability Sixpack ► Normal….

Confidence Interval of Process Capability Indices Antenna Diameter.mtw from CIC3640 is used as the example

• Menu: Stat ► Quality Tools ► Capability Analysis ► Normal…

Documents

CIC3640 • SPC and Capabilitylearningmedia0.motorolasolutions.com/services/edu/...Calculate the Capability Indices Step 8. Make recommendations for process improvement. Cautions in