Sample sizes (draft)

Currently TrueDelta publicly posts Vehicle Reliability Survey results when there have been responses for at least 20 vehicles owned for at least 80 total months. In comparison, Consumer Reports’ minimum sample is 100 vehicles, with no minimum number of months of ownership. One hundred sounds a lot more impressive than 20. And they do love to brag about the size of their… More →

Corruption in dealer satisfaction surveys

“Don’t Coach Me on how to Answer your Stupid Survey,” Mrad writes over at Volksbloggin, a VW-focused blog. The object of his ire: dealers that ask you to give them perfect marks on sales and service satisfaction surveys conducted by the manufacturer. I’ve come across this myself, and read about it often on various forums. Why is this survey process… More →

Assumptions made by the CNW “lifetime energy cost” report

A few weeks ago I posted a critique of CNW’s lifetime energy cost report, which controversially concluded that a Prius uses up more energy per mile over its lifetime than a Hummer. My critique then was based simply on the ridiculously high cost per mile figures the report included. From this I inferred that some untenable assumptions were made by… More →

Without a random sample, aren’t TrueDelta’s results biased?

TrueDelta doesn’t gather its data from a random sample of vehicle owners. Worse, many people join TrueDelta after reading about it on a forum, and many people only visit automotive forums when they have a problem with their car. For these two reasons, I’m often asked “Don’t you think your research is going to be very biased?. The short answer: no… More →

The anti-hybrid “dust-to-dust” cost study that just won’t die, but needs to

To me, hybrids make intuitive sense. Why not recover some of the energy that will otherwise be converted to heat by the brakes? But some people hate hybrids. And for them CNW’s ‘Dust to Dust Automotive Energy Report’ has been a godsend. It claims that once you consider all of the energy costs that go into a vehicle, from development… More →

Reliability stats from Warranty Direct

A month or so ago extended warranty provider Warranty Direct released claim rates by manufacturer. Since it was largely (or even entirely) based on UK policies, this study only received attention across the water. Then, yesterday, Mazda USA decided to tout its top ranking. And I’m being asked what I think of these results. On the face of it, an extended… More →