Analysis now includes some repair trips where parts were ordered

No part of TrueDelta’s Vehicle Reliability Survey (with the exception of email delivery) causes more trouble than the process of reporting a repair trip where parts were ordered and then another when the parts are installed. Often people only report one and not the other. How should this be handled when analyzing the data?

To date, analyses have only included repair trips that included a successful repair. So if the only outcome was that parts were ordered, the trip was not included. This caused two problems:

  1. Some people forget to report the second trip, probably because they remember already reporting the problem.
  2. Sometimes it takes a long time–nearly a year in some cases–for the parts to come in and be installed. Meanwhile, the owner is living with the problem.

In both cases past analyses risk underestimating repair rates. So, starting with this month’s results, repair trips where parts were ordered will be included in the analysis until the parts are installed, at which point only the latter trip will be included. This doesn’t affect many models, and most of those it does affect it affects only a little, but it nevertheless makes the results more accurate.

The revised analysis also will warn of high repair rates more quickly with affected new models. When a model is new, parts for common problems are often on backorder. And even when parts are available, the repair trips for newly introduced models tend to only involve ordering parts, with the parts installed a month or two later. The vehicles simply haven’t been around long enough to go through the typical cycle of going to the shop, ordering parts, then returning to the shop to have these parts installed. With the old method, the results wouldn’t reflect these problems until the parts became available and were installed. With the new method, problems will have an impact on the reported repair rates with less of a delay.¬†

There is one other benefit.¬†Most of the responses I’m still waiting for from participants involve open issues. Hopefully these members will still respond. But in nearly all cases they’ll report that the repair was completed in a previously unreported repair trip. The revised analysis anticipates this response, allowing preliminary results to be posted now.

  • Michael – One of the things I remember that you talked about True Delta being able to do was give people an idea how many days per year a car might be in the shop. Doesn’t that argue for having both trips reported. That’s 2 days in the shop, min.

    That also argues to having reflashes and TPS resets included as well. Each results in a trip to the shop, if not a day to diagnose first before the reset.

    What do you think?

  • Michael

    This all makes sense. I’ll be reporting a larger number of statistics in the future, which will include different things. Right now I’m focusing on a single statistic that requires a smaller sample size than most others would. “Days in the shop” will have large outlying values that would seriously distort a result based on a small sample.