Comments on: Span – GE’s Variation Weapon http://lssacademy.com/2007/04/12/span-ges-variation-weapon/ Lean Manufacturing, Six Sigma, Lean Six Sigma, and Kaizen Sat, 12 May 2012 15:25:36 +0000 hourly 1 http://wordpress.org/?v=3.3.2 By: Sion Weaver http://lssacademy.com/2007/04/12/span-ges-variation-weapon/comment-page-1/#comment-4162 Sion Weaver Tue, 12 Jan 2010 00:15:11 +0000 http://lssacademy.com/?p=212#comment-4162 Span is used simply to measure the fit. If you improve on an average, you can still have the product arriving too early or too late. Like Dave mentioned reduce the Span is the target. As Span is reduced the variation goes down and performance is improved. As GE pushed Six Sigma into management and service units, Span was introduced as a way to look at variation. Much of the data in service and management can be non normal. If the customer needs the delivery in one week then the Span between 2 and 17 would include deliveries too early and too late. 2days--------------------Span------------------17 days Bring deliveries where they are always 7days or 8 days and the customer is getting what they need. Span is used simply to measure the fit. If you improve on an average, you can still have the product arriving too early or too late. Like Dave mentioned reduce the Span is the target. As Span is reduced the variation goes down and performance is improved.

As GE pushed Six Sigma into management and service units, Span was introduced as a way to look at variation. Much of the data in service and management can be non normal.

If the customer needs the delivery in one week then the Span between 2 and 17 would include deliveries too early and too late.
2days——————–Span——————17 days

Bring deliveries where they are always 7days or 8 days and the customer is getting what they need.

]]> By: Ryan Meyers http://lssacademy.com/2007/04/12/span-ges-variation-weapon/comment-page-1/#comment-2672 Ryan Meyers Wed, 12 Nov 2008 23:01:34 +0000 http://lssacademy.com/?p=212#comment-2672 jjeii2np2hep0f60 jjeii2np2hep0f60

]]> By: Ron Pereira http://lssacademy.com/2007/04/12/span-ges-variation-weapon/comment-page-1/#comment-1068 Ron Pereira Fri, 19 Oct 2007 23:50:54 +0000 http://lssacademy.com/?p=212#comment-1068 Thanks for the comment Dave. As with all stats the key, in my opinion, is to use them to solve business problems. Span is great when dealing with non normal data since more traditional descriptive statistics such as standard deviation begin to lose their power when dealing with non parametric data. If data are normal I would not personally use Span... I would use standard deviation as my measure of dispersion. Would you agree? Thanks for the comment Dave. As with all stats the key, in my opinion, is to use them to solve business problems.

Span is great when dealing with non normal data since more traditional descriptive statistics such as standard deviation begin to lose their power when dealing with non parametric data.

If data are normal I would not personally use Span… I would use standard deviation as my measure of dispersion.

Would you agree?

]]> By: Dave Kershaw http://lssacademy.com/2007/04/12/span-ges-variation-weapon/comment-page-1/#comment-1067 Dave Kershaw Thu, 18 Oct 2007 23:42:44 +0000 http://lssacademy.com/?p=212#comment-1067 With respect, I think you're both missing the point. If a data set exhibits normal distribution then stats are fine for making predictions. The beauty of span is it doesn't try to make predictions but acts as an indicator of how good / poor performance is. Then act to reduce the span. I'd appreciate feedback though, always willing to learn so if I'm talking nonsense tell me. With respect, I think you’re both missing the point. If a data set exhibits normal distribution then stats are fine for making predictions. The beauty of span is it doesn’t try to make predictions but acts as an indicator of how good / poor performance is. Then act to reduce the span. I’d appreciate feedback though, always willing to learn so if I’m talking nonsense tell me.

]]> By: Ron Pereira http://lssacademy.com/2007/04/12/span-ges-variation-weapon/comment-page-1/#comment-392 Ron Pereira Thu, 26 Apr 2007 01:16:00 +0000 http://lssacademy.com/?p=212#comment-392 Thanks for the comment Sushil. The issue is the data I used for this graph is normal. I used Minitab to generate randon normal data. I simply wanted to show how you can calculate span with some data. In hindsight I should have used non normal data in my example and then showed how taking the difference between 95 and 5 percentile gives us span. Thanks for the feedback I hope to see you check back in to keep me honest! Thanks for the comment Sushil. The issue is the data I used for this graph is normal. I used Minitab to generate randon normal data. I simply wanted to show how you can calculate span with some data. In hindsight I should have used non normal data in my example and then showed how taking the difference between 95 and 5 percentile gives us span. Thanks for the feedback I hope to see you check back in to keep me honest!

]]> By: Anonymous http://lssacademy.com/2007/04/12/span-ges-variation-weapon/comment-page-1/#comment-393 Anonymous Wed, 25 Apr 2007 16:26:00 +0000 http://lssacademy.com/?p=212#comment-393 Hi Ron,<BR/>Your method of using the normality plot is incorrect. The reference lines at 5 and 95 are drawn based on the fitted line and not the actual data. So, for data that is non-normal, the fit is bad and your results are going to be wrong. To convince yourself of this repeat the extraction using reference lines at 25 and 75 percentiles and compare to the 1st and 3rd quartile levels from a boxplot.<BR/><BR/>Regards,<BR/>Sushil Hi Ron,
Your method of using the normality plot is incorrect. The reference lines at 5 and 95 are drawn based on the fitted line and not the actual data. So, for data that is non-normal, the fit is bad and your results are going to be wrong. To convince yourself of this repeat the extraction using reference lines at 25 and 75 percentiles and compare to the 1st and 3rd quartile levels from a boxplot.

Regards,
Sushil

]]> By: Ron Pereira http://lssacademy.com/2007/04/12/span-ges-variation-weapon/comment-page-1/#comment-394 Ron Pereira Sat, 14 Apr 2007 14:26:00 +0000 http://lssacademy.com/?p=212#comment-394 Excellent JWDT! Thanks for sharing... I am going to give it a shot with my next VSM. Cheers! Excellent JWDT! Thanks for sharing… I am going to give it a shot with my next VSM. Cheers!

]]> By: JWDT http://lssacademy.com/2007/04/12/span-ges-variation-weapon/comment-page-1/#comment-395 JWDT Sat, 14 Apr 2007 04:39:00 +0000 http://lssacademy.com/?p=212#comment-395 Ron,<BR/>I have shown SPAN (P5/P95) on VSM's for operations that have a lot of variation within the processing time. Especially in the Transactional settings. Primarily used it to show where the point kaizens or string kaizens should be performed for the max impact. May find that you need to show P1/P99 for tighter processes or where standard work has eliminated a lot of the variation in some ops.<BR/>JWDT Ron,
I have shown SPAN (P5/P95) on VSM’s for operations that have a lot of variation within the processing time. Especially in the Transactional settings. Primarily used it to show where the point kaizens or string kaizens should be performed for the max impact. May find that you need to show P1/P99 for tighter processes or where standard work has eliminated a lot of the variation in some ops.
JWDT

]]> By: Ron Pereira http://lssacademy.com/2007/04/12/span-ges-variation-weapon/comment-page-1/#comment-396 Ron Pereira Fri, 13 Apr 2007 16:04:00 +0000 http://lssacademy.com/?p=212#comment-396 From Wikipedia:<BR/><BR/>In the United States, the residents of the state of Hawaii and the territories of Guam and the Commonwealth of the Northern Mariana Islands (CNMI) consume the most Spam per capita. On average, each person on Guam consumes 16 tins of Spam each year and the numbers at least equal this in the CNMI. Guam, Hawaii, and Saipan, the CNMI's principal island, have the only McDonald's restaurants that feature Spam on the menu. One popular Spam dish in Hawaii is Spam musubi, in which cooked Spam is combined with rice and nori seaweed and classified as onigiri.<BR/><BR/>Oh wait... that is Spam not Span! Sorry to add to the confusion. From Wikipedia:

In the United States, the residents of the state of Hawaii and the territories of Guam and the Commonwealth of the Northern Mariana Islands (CNMI) consume the most Spam per capita. On average, each person on Guam consumes 16 tins of Spam each year and the numbers at least equal this in the CNMI. Guam, Hawaii, and Saipan, the CNMI’s principal island, have the only McDonald’s restaurants that feature Spam on the menu. One popular Spam dish in Hawaii is Spam musubi, in which cooked Spam is combined with rice and nori seaweed and classified as onigiri.

Oh wait… that is Spam not Span! Sorry to add to the confusion.

]]> By: Jon Miller http://lssacademy.com/2007/04/12/span-ges-variation-weapon/comment-page-1/#comment-397 Jon Miller Fri, 13 Apr 2007 15:20:00 +0000 http://lssacademy.com/?p=212#comment-397 To add to the confusion, span time is sometimes used to refer to lead time.<BR/><BR/>Span, wonderful span. To add to the confusion, span time is sometimes used to refer to lead time.

Span, wonderful span.

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