Season Three Summary

There were 24 episodes in season three, many with more than one patient. One Day, One Room was excluded to leave 23. House was not present for Airborne, and Chase was absent for most of Human Error.

Patients treated: 29
Lives saved: 26
There were two patients each in Meaning, Fools For Love, Half-Wit counting the patient whose records House stole, Fetal Position, Act Your Age, and Family.
In Informed Consent and Que Sera Sera the patients died because their illnesses were incurable, and in House Training the team killed the patient by misdiagnosing her.

House: 25 diagnoses + 58 credits - 5 errors = 78 total
Chase: 6 diagnoses + 28 credits - 3 errors = 31 total
Cameron: 3 diagnoses + 20 credits - 0 errors = 23 total
Foreman: 3 diagnoses + 24 credits - 4 errors = 23 total

My conclusions: Over three seasons the Department of Diagnostic Medicine treated 80 patients and saved the lives of 68 of them.
Everyone had more credits in the third season, which I think has more to do with me than with the show. Even taking that into account, all of the Housepets improved this season. Chase grew the most this season, developing his observational skills and making the same intuitive leaps that House does to come up with diagnoses. Both Cameron and Foreman contributed more to the diagnostic process, but Foreman's error rate increased. As in season two, Cameron and Foreman appear to be equal in their performance with Chase proving to be the best diagnostician of the three. It's not a large lead, but it is definitely there.