The writers below are ranked based on the average quality of their episodes after taking into account when the episodes aired. Only writers who wrote at least four episodes are in the list. Writers who wrote or co-wrote only one, two, or three episodes each are combined into the "Other Writers" category. Writers are given half credit for episodes that they co-write with another person except for "Doomed," for which each of the writers gets one-third credit. For the purposes of best and worst episode, writers get full credit / blame for solo and co-written episodes. Teams who write with each other exclusively are treated as if they are a single writer.
The number in parentheses can be thought of as being the "Joss bonus." It represents how many more points episode written by this person would get if it were written by Joss Whedon instead. Lower numbers suggest that the writer is almost as good as Joss Whedon. High numbers suggest that Joss Whedon could have done a much better job. By definition, Joss Whedon gets a 0 on this statistic. This interpretation assumes that the writer of the episode is the main cause of the episode's quality.
Wrote 23.5 Episodes
Best Episode: "Once More, with Feeling" (121.50 points)
Worst Episode: "Ted" (62.72 points)
Wrote 4 Episodes
Best Episode: "Conversations with Dead People" (89.39 points)
Worst Episode: "Never Leave Me" (66.16 points)
Wrote 12 Episodes
Best Episode: "Passion" (Ty King: 99.05 points)
Worst Episode: "I, Robot — You, Jane" (Ashley Gable & Thomas A. Swyden: 55.38 points)
Wrote 7.5 Episodes
Best Episode: "Angel" (80.72 points)
Worst Episode: "Teacher's Pet" (57.26 points)
Wrote 21.33 Episodes
Best Episode: "The Wish" (91.84 points)
Worst Episode: "Bad Eggs" (57.37 points)
Wrote 5 Episodes
Best Episode: "Phases" (67.09 points)
Worst Episode: "Never Kill A Boy on the First Date" (63.53 points)
Wrote 19.33 Episodes
Best Episode: "Conversations with Dead People" (89.39 points)
Worst Episode: "Doublemeat Palace" (53.93 points)
Wrote 15 Episodes
Best Episode: "Fool for Love" (90.68 points)
Worst Episode: "As You Were" (60.54 points)
Wrote 8 Episodes
Best Episode: "Tabula Rasa" (94.74 points)
Worst Episode: "Listening to Fear" (61.29 points)
Wrote 5 Episodes
Best Episode: "Seeing Red" (74.71 points)
Worst Episode: "All the Way" (61.62 points)
Wrote 14.33 Episodes
Best Episode: "Grave" (83.70 points)
Worst Episode: "Go Fish" (58.21 points)
Wrote 6 Episodes
Best Episode: "Smashed" (68.16 points)
Worst Episode: "Empty Places" (63.15 points)
Overall, the writers account for 19.9% of episode quality.