{"id":140,"date":"2014-02-02T14:34:47","date_gmt":"2014-02-02T14:34:47","guid":{"rendered":"http:\/\/www.eversholt.org.uk\/blog\/?p=140"},"modified":"2014-02-02T14:34:47","modified_gmt":"2014-02-02T14:34:47","slug":"is-it-fixed-yet","status":"publish","type":"post","link":"https:\/\/www.eversholt.org.uk\/blog\/is-it-fixed-yet\/","title":{"rendered":"Is It Fixed Yet?"},"content":{"rendered":"

This is the first in a series of posts about a calculation that worried me for years – about fifteen years. The question occurred to me when my car, a newish company car, broke. It stopped going along. Eventually it started again and I took it to the garage. They changed some parts, presented a big bill, and I drove away. Next week, the car stopped again. After a few minutes, it started. I took it back to the garage, they changed some more parts, and I paid another big bill. Next week… you get the idea. It was driving away from the garage for the third time that I wondered, “How do I work out whether the car is really repaired?” How much testing do I have to do before I trust the car again?<\/p>\n

It took me 15 years to work out the answer. I tried collaborating with four different people, and couldn’t solve it. Then, one day, Eureka.<\/p>\n

This all happened when I was working for Sun Microsystems, so if there is any intellectual property in the idea, it belongs to them, or now to Oracle. I don’t think a patent was ever applied for – it was in a chaotic time close to when I left Sun, and it’s not in this list.<\/a> But, it’s old enough now that I don’t think anyone will mind if I publish it. I’ve never seen the result anywhere else, although I’m a bit out of touch with the field now.<\/p>\n

The eventual result is applicable to things that break, and also new products with design flaws. It seems quite general.<\/p>\n

Future posts here will explain the idea and (if I get my act together) present an online calculator for working out the chance that a problem has been fixed by a repair, given a pattern of test failures and passes both before and after the repair. But I haven’t written that yet.<\/p>\n","protected":false},"excerpt":{"rendered":"

This is the first in a series of posts about a calculation that worried me for years – about fifteen years. The question occurred to me when my car, a newish company car, broke. It stopped going along. Eventually it started again and I took it to the garage. They changed some parts, presented a […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[7],"tags":[],"class_list":["post-140","post","type-post","status-publish","format-standard","hentry","category-fixed-yet"],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/www.eversholt.org.uk\/blog\/wp-json\/wp\/v2\/posts\/140","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.eversholt.org.uk\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.eversholt.org.uk\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.eversholt.org.uk\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.eversholt.org.uk\/blog\/wp-json\/wp\/v2\/comments?post=140"}],"version-history":[{"count":5,"href":"https:\/\/www.eversholt.org.uk\/blog\/wp-json\/wp\/v2\/posts\/140\/revisions"}],"predecessor-version":[{"id":145,"href":"https:\/\/www.eversholt.org.uk\/blog\/wp-json\/wp\/v2\/posts\/140\/revisions\/145"}],"wp:attachment":[{"href":"https:\/\/www.eversholt.org.uk\/blog\/wp-json\/wp\/v2\/media?parent=140"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.eversholt.org.uk\/blog\/wp-json\/wp\/v2\/categories?post=140"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.eversholt.org.uk\/blog\/wp-json\/wp\/v2\/tags?post=140"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}