{"id":3684,"date":"2014-07-23T13:50:00","date_gmt":"2014-07-23T13:50:00","guid":{"rendered":"http:\/\/www.saasoft.com\/blog\/?p=3684"},"modified":"2014-07-23T13:50:00","modified_gmt":"2014-07-23T13:50:00","slug":"perfect-storm","status":"publish","type":"post","link":"https:\/\/hcse.blog\/?p=3684","title":{"rendered":"Perfect Storm"},"content":{"rendered":"

\"lightning_strike_150_wht_5809\"<\/a>[Drrrrring Drrrrring<\/strong>]<\/p>\n

<Bob><\/em> Hi Lesley! How are you today?<\/p>\n

<Leslie><\/em> Hi Bob.\u00a0 Really good.\u00a0 I have just got back from a well earned holiday so I am feeling refreshed and re-energised.<\/p>\n

<Bob><\/em> That is good to hear.\u00a0 It has been a bit stormy here over the past few weeks.\u00a0 Apparently lots of\u00a0 hot air hitting cold reality and forming a fog of disillusionment and storms of protest.<\/p>\n

<Leslie><\/em> Is that a metaphor?<\/p>\n

<Bob><\/em> Yes!\u00a0 A good one do you think? And it leads us into our topic for this week. Perfect storms.<\/p>\n

<Leslie><\/em> I am looking forward to it.\u00a0 Can you be a bit more specific?<\/p>\n

<Bob><\/em> Sure.\u00a0 Remember the ISP exercise where I asked you to build a ‘chaos generator’?<\/p>\n

<Leslie><\/em> I sure do. That was an eye-opener!\u00a0 I had no idea how easy it is to create chaotic performance in a system – just by making the Flaw of Averages error and adding a pinch of variation. Booom!<\/p>\n

<Bob><\/em> Good. We are going to use that model to demonstrate another facet of system design.\u00a0 How to steer out of chaos.<\/p>\n

<Leslie><\/em> OK – what do I need to do.<\/p>\n

<Bob><\/em> Start up that model and set the cycle time to 10 minutes with a sigma of 1.5 minutes.<\/p>\n

<Leslie><\/em> OK.<\/p>\n

<Bob><\/em> Now set the demand interval to 10 minutes and the sigma of that to 2.0 minutes.<\/p>\n

<Leslie><\/em> OK. That is what I had before.<\/p>\n

<Bob><\/em> Set the lead time upper specification limit to 30 minutes. Run that 12 times and record the failure rate.<\/p>\n

<Leslie><\/em> OK.\u00a0 That gives a chaotic picture!\u00a0 All over the place.<\/p>\n

<Bob><\/em> OK now change just the average of the demand interval.\u00a0 Start with a value of 8 minutes, run 12 times, and then increase to 8.5 minutes and repeat that up to 12 minutes.<\/p>\n

<Leslie><\/em> OK. That will repeat the run for 10 minutes. Is that OK.<\/p>\n

<Bob><\/em> Yes.<\/p>\n

<Leslie><\/em> OK … it will take me a few minutes to run all these.\u00a0 Do you want to get a cup of tea while I do that?<\/p>\n

<Bob><\/em> Good idea.<\/p>\n

[5 minutes later]<\/strong><\/p>\n

<Leslie><\/em> OK I have done all that – 108 data points. Do I plot that as a run chart?<\/p>\n

<Bob><\/em> You could.\u00a0 I suggest plotting as a scattergram.<\/p>\n

<Leslie><\/em> With the average demand interval on the X axis and the Failure % on the\u00a0 Y axis?<\/p>\n

<Bob><\/em> Yes. Exactly so. And just the dots, no lines.<\/p>\n

<Leslie><\/em> OK. Wow! That is amazing!\u00a0 Now I see why you get so worked up about the Flaw of Averages!<\/p>\n

<Bob> What you are looking at is called a performance curve.\u00a0 Notice how steep and fuzzy it is. That is called a chaotic transition. The perfect storm.\u00a0 And when fall into the Flaw of Averages trap we design our systems to be smack in the middle of it.<\/p>\n

<Leslie><\/em> Yes I see what you are getting at.\u00a0 And that implies that to calm the chaos we do not need very much resilient flow capacity … and we could probably release that just from a few minor design tweaks.<\/p>\n

<Bob><\/em> Yup.<\/p>\n

<Leslie><\/em> That is so cool. I cannot wait to share this with the team. Thanks again Bob.<\/p>\n","protected":false},"excerpt":{"rendered":"

[Drrrrring Drrrrring] <Bob> Hi Lesley! How are you today? <Leslie> Hi Bob.\u00a0 Really good.\u00a0 I have just got back from a well earned holiday so I am feeling refreshed and re-energised. <Bob> That is good to hear.\u00a0 It has been a bit stormy here over the past few weeks.\u00a0 Apparently lots of\u00a0 hot air hitting … <\/p>\n

Continue reading “Perfect Storm”<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[8,20,26,28,36,45,46],"tags":[],"class_list":["post-3684","post","type-post","status-publish","format-standard","hentry","category-bobles","category-flow","category-isp","category-metaphors","category-resilient","category-what","category-teach"],"_links":{"self":[{"href":"https:\/\/hcse.blog\/index.php?rest_route=\/wp\/v2\/posts\/3684","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/hcse.blog\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/hcse.blog\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/hcse.blog\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/hcse.blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=3684"}],"version-history":[{"count":0,"href":"https:\/\/hcse.blog\/index.php?rest_route=\/wp\/v2\/posts\/3684\/revisions"}],"wp:attachment":[{"href":"https:\/\/hcse.blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=3684"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/hcse.blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=3684"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/hcse.blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=3684"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}