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I hope this is the right place where to formulate this question. In a basic course in statistics we learn how to calculate the mean life time of an electronic device. Home appliances are electronic device of course, but all that we know when we buy one is the time length of warranty.

What is the relation of mean life time and warranty time in the home appliances? or better how is calculated the warranty time? What I am interested is how to calculate the probability that an appliance will brake within the warranty time.

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  • $\begingroup$ Note that life expectancy and mean lifetime are the same only under certain conditions. $\endgroup$ Nov 14, 2012 at 11:13
  • $\begingroup$ Different companies have different policies for offering a warranty. The mean lifetime is the average lifetime of a device and this usually does not coincide with the warranty. The warranty is typically chosen as a quantile in the left-tail of the distribution of failure times (e.g. $5\%$). This means that about 5% of the products will fail by that time. This value is chosen based on several criteria that consider marketing strategies and the aimed profit. For instance, expensive brands typically offer a long warranty (larger quantile, maybe $10%$ or more) for marketing purposes. $\endgroup$
    – user10525
    Nov 14, 2012 at 12:17
  • $\begingroup$ In addition, the definition of warranty varies among companies. Some of them offer replacement of the device by a new one. Some others ask you to bring the device to their repair labs and wait until their engineers fix it. This, of course, implies a cost that will be included in final price of the product. Moreover, the choice of this value is typically a trade secret. (BTW, intesting question +1) $\endgroup$
    – user10525
    Nov 14, 2012 at 12:28
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    $\begingroup$ @Procrastinator Good answer, if you put it in form of answer I will give +1 for sure. $\endgroup$
    – emanuele
    Nov 14, 2012 at 13:26
  • $\begingroup$ @Procrastinator I made a little calculation. If we take a definition of warranty as the time where the 0.05 of the whole number of appliances selled will fail, and 1 year of warranty and an exponential decay for appliences, then this means that the mean life time will be more then 19 years. Is this true? $\endgroup$
    – emanuele
    Nov 14, 2012 at 14:07

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