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How accurate are we?

We ask you to trust our numbers, so here is how well they hold up when we test them. These figures are measured, not claimed. When one of them gets worse, it gets worse on this page too.

Being straight with you about this page

The measurement harness is built but has not been run against a hand-labelled set yet, so we are not going to print numbers here and imply they mean something. What follows is exactly what we will measure and how, published now so the method is fixed before we see the results rather than chosen afterwards to flatter them.

Does trust weighting actually beat star averaging?

The question the whole product rests on.

We take the people best placed to judge a car, owners who have kept it over a year and driven it more than 10,000 km, and treat what they think as the answer. Then we throw their reviews away and see how close we can get using only the ordinary reviews that are left.

This is not circular, because the target is defined by information the estimate never sees. If weighting by trust did not help, counting every review the same would do just as well, and the whole premise of this site would be wrong.

Every review counts the same

The baseline every review site uses today.

Weighted by which site it came from

Fixed priors per source.

Weighted by how much each can be trusted

The default here.

What we will publish, and what it means

What we measureIn plain termsStatus
Right car, right variantHow often a review lands on the exact variant it describes.Harness built, gold set pending
Right topicHow often a sentence is filed where a person would file it.Harness built, gold set pending
Fake reviews caughtHow much of a known-fake set gets pushed down before it can move a score.Classifier not yet trained
Honest rangesWhether our 80% range contains the answer 80% of the time.Harness built, run pending
Serving speedHow long a verdict page takes to answer.Measured: 29 ms at the 95th percentile

What we already know we are bad at

Plenty of Indian reviews are written in a mix of Hindi and English, often typed in the Latin alphabet. Our current topic extraction is a keyword and rule system built around English words, so it understands those noticeably less well. A topic score built mostly from them is weaker than one built from English reviews. We would rather tell you that than average the problem out of sight, and it is the first thing a trained classifier has to fix.

None of this means our verdict is the truth. There is no such thing as the objectively correct opinion of a car. What we can show you is our working, so you can decide how much of it to believe. See how a score is worked out.