QIMacros Test Results

Expected QI Macros Results and Comparison to Minitab 12 or other Resources

Table of Contents

Chart Page # Expected Differences 2 Control Charts Attribute Charts - c, u, p, np 3 Variable Charts - Xmr, XbarR, XandS, XmR Trend, Xmedian

7

Cusum 17 Moving Average 18 EWMA 19 Control Chart Stability Rules 21 Control Chart Stability Tests 23 Histogram with Cp and Cpk 36 Frequency Histogram 40 Capability 5 pack 41 Other Charts Pareto 42 Run 43 Scatter 44 Box and Whisker 45 Mulitvari Chart 46

©MMVI KnowWare International Inc. www.qimacros.com 1

Expected Differences Stability Analysis Both the QI Macros and Minitab let you define what stability rules you want to use. The QI Macros defaults to Montgomery's rules but lets you select from Juran, AIAG and Western Electric rules. You can also further customize rules in the QI Macros. See http://www.qimacros.com/free-excel-tips/control-chart-rules.html Minitab requires you to define the rules you want to use each time you run a chart. The QI Macros offer additional tests that Minitab does not. Minitab also treats trends differently than the QI Macros. For example, one common set of rules is 6 points in a row increasing or decreasing. Once you have 6 points in a row that meet these criteria, the QI Macros will turn all 6 points red. Minitab will not turn any points red until the 7th point and then will only turn the 7th point red. Upper and Lower control limits on u, p, and XandS charts – since the sample size on these charts vary, the upper and lower control limits vary (from point to point). Minitab displays the UCL and LCL for the last point. The QI Macros display the UCL and LCL for the 3rd to the last point. Note the control limit lines are the same, only the value displayed is different. Also, the center lines are both the same since these do not vary. Histogram - Standard Deviation calclation The QI Macros uses the standard deviation calculation of Microsoft Excel. Minitab uses a different calculation which returns slightly different results. The standard deviation difference will cause slight differences in the following calculations: Pp, Ppk, Z score and Expected PPM Histogram Cp, Cpk calculation when subgroup size is 3 The difference in the two calculations is the constant used in the sigma estimator calculation. This effects Cp and Cpk but not Pp and Ppk. Per Juran and Montgomery, the QI Macros use a constant of 1.693 when there are 3 subgroups. It looks like Minitab is using something like 1.093. We do not know where this constant comes from and believe it to be an error in Minitab. Cusum and Moving Average Chart Control Limits Control limits are slightly different because QI Macros uses standard deviation while Minitab uses sigma estimator.


C Chart QI Macros c Chart

Minitab c Chart


u Chart QI Macros u chart

Minitab u chart

UCL / LCL differences. See notes regarding expected differences on page 2.


p Chart QI Macros p chart

Minitab p chart

UCL / LCL differences. See notes regarding expected differences on page 2.


np Chart QI Macros np Chart

Minitab np chart

See note regarding difference in stability rules on page 2.


XmR Chart QI Macros X chart

Minitab X chart



QI Macros Range Chart

Minitab R chart



XbarR Chart

QI Macros Xbar chart

Minitab Xbar chart


QI Macros R chart

Minitab R chart


XandS Chart

QI Macros X chart

Minitab X chart


QI Macros S chart

Minitab S chart


XmR Trend

QI Macros Trend chart

Minitab Trend chart


QI Macros R chart

Minitab R chart N/A


Xmedian R – Single Column of Data QI Macros X Chart

QI Macros R Chart

Minitab does not offer median charts


Xmedian R – Multiple Columns of Data QI Macros X Chart

QI Macros R Chart

Minitab does not offer median charts


Cusum Chart

QI Macros Cusum Chart - Target = 10

Minitab Cusum Chart - Target =10

Control limits are slightly different because QI Macros uses standard deviation while Minitab uses sigma estimator.


Moving Average Chart

QI Macros Trend chart

Control limits are slightly different because QI Macros uses standard deviation while Minitab uses sigma estimator.


Estimated Moving Weighted Average Chart QI Macros

Minitab


QI Macros EWMA R chart

Minitab Moving Range Chart Run separately


Control Chart Stability Rules QI Macros 2006 and Previous Versions are based on Montgomery's rules.

QI Macros 2007 - Lets you choose rules from various sources or customize your own. Montgomery's rules are used as the default rules.


Minitab Attribute and Range Chart Rules

Minitab X chart Rules


Control Chart Stability Tests

1 point above UCL

QI Macros

Minitab


1 point below LCL QI Macros

Minitab


2 out of 3 points above 2 sigma QI Macros

Minitab - does not perform this test on attribute charts


2 out of 3 points below -2 sigma

QI Macros



4 out of 5 points above 1 sigma QI Macros



4 out of 5 points below - 1 sigma

QI Macros



8 points in a row above Center Line -

Minitab - uses 9 points not 8 (QI Macros - set to Juran rules to use 9)


8 points in a row below Center Line QI Macros

Minitab - uses 9 points not 8 (QI Macros - set to Juran rules to use 9)


6 points in a row increasing QI Macros

Minitab - will not turn this condition red until the 7th point and then will only turn the 7th and additional points red


6 points in a row decreasing QI Macros



15 points in a row inside =- 1 sigma (hugging) QI Macros



14 points in a row alternating up and down QI Macros



8 points in a row outside =- 1 sigma



Histograms and Capability Analysis Explanation of Differences Standard Deviation calculation. The QI Macros uses the standard deviation calculation of Microsoft Excel. Minitab uses a different calculation which returns slightly different results. The standard deviation difference will cause slight differences in the following calculations: Pp, Ppk, Z score and Expected PPM Data Source: Montgomery, Intro to SPC, 4th Ed., pgs. 353-358 USL = 346 LSL = 200


QI Macros Histogram - increase decimals on data in Hist data sheet from 1 to 2 to more easily compare results.

Minitab Histogram


Second Histogram with Different Cp and Pp, Cpk and Ppk Data Source: Montgomery Intro to SPC (5th) pg 200 USL = 2 LSL = 1


QI Macros Histogram

Minitab Histogram


QI Macros Frequency Histogram

Minitab Capability Analysis


QI Macros X chart Templates using Data set 1

Minitab Capability Six Pack


Pareto Chart QI Macros Pareto Chart

Minitab Pareto Chart


Run Chart QI Macros Run Chart

Minitab Run Chart


Scatter Diagram

QI Macros Scatter Diagram and Metrics on Calculation sheet

Minitab Scatter Diagram


Box and Whisker

QI Macros Box and Whisker

Minitab Box and Whisker


Multivari Chart QI Macros

Minitab - no Multivari chart


Documents

QIMacros Test Results