Well, it had to happen at some point: a usually reliable model requires multiple repair trips for one owner. In statistics, this is known as an “outlier.” The question for me: how to handle them? Leaving outliers as they are can distort the results, especially with small sample sizes. In the most extreme case from the upcoming August results, I… More →
Category: Research Methods
Research Methods
Proof of concept: reliability results for the Nissan Versa and Saturn Aura
With frequent surveys and fast analysis, TrueDelta’s research process has been designed to provide reliability information soon after a new model launches. And so the May results include the first reliability statistics you’ll find anywhere on the Nissan Versa and Saturn Aura.
Fusion beats Camry and Accord?
For a few months now Ford has been touting the “Fusion Challenge.” In a pair of Ford-sponsored events, 1,000 subscribers to Car and Driver and Road & Track rated the Ford Fusion higher than the Toyota Camry and Honda Accord. I can’t decide what concerns me more, that the magazines had Ford pay them to conduct the events or that… More →
Why TrueDelta excludes inconsistent respondents from the analysis
TrueDelta only recently started collecting data on the 2007 Acura MDX. So far, the 32 owners who have responded have reported only one trip to the shop that included a successful repair. This repair trip would be included in the analysis, except for one thing: the repair was reported for January, and the owner in question did not respond for… More →
Issue tracking added to the Vehicle Reliability Survey
Another quarter, another set of tweaks to the Vehicle Reliability Survey. This time around, I’ve sought to address two common problems with responses. First off, people often report multiple issues at the same time. The form has been revised to make it clearer that the top half of the form should be filled out separately for each repair trip, while… More →
Time to clean the data!
Well, except for a few stragglers data collection is done for the quarter. There’s more of it than ever before. Which also means there’s more of it to clean than ever before. First, a bit on growth. Last month 5,064 cars were surveyed. Of these, a survey was completed for 2,183 of them. Which works out to a 43 percent… More →
Long-term road tests: insufficient sample
For years the car magazines have conducted long-term road tests (links from Google). The manufacturer gives them a car to drive for 30,000 to 40,000 miles, and they write up both their impressions of what the car is like to drive and what broke. No problem with the first bit: you might learn more about a car when you drive… More →
Consumer Reports adopts one of my less intelligent suggestions
I’ve been very critical of the survey question Consumer Reports uses to gather its vehicle reliability data, most notably in this editorial. They’re aware of my critiques, and I’ve been wondering whether they’d improve their survey as a result. Well, this year’s survey is out, so I have my answer.
The Economist demonstrates how not to calculate fuel economy
Over at Autoblog I read that The Economist has had a blinding flash of the obvious and discovered that a used Civic is less expensive than a new Prius. But there’s more to the story: the author also found that changing the oil and air filter boosted the used Civic’s fuel economy from 34 to 40 mpg. This set off… More →
1,200 responses in the first 26 hours
Whenever the quarterly survey email goes out, the one where a response is required for every vehicle in the active panel, I pay very close attention to the response rate. The May results potentially include far more models than the previous two sets of results, and I’m personally very excited about this. But the sample sizes for many models will… More →