Speech (Fallout 3)

Speech is a skill It determines the chance to succeed in a speech challenge.

Initial level

 * $$\text{Initial level}=2+(2\times\text{Charisma})+\left\lceil\frac{\text{Luck}}{2}\right\rceil$$

Example: A starting Charisma of 5 and Luck of 5.
 * $$2+(2\times5)+\left\lceil\frac{5}{2}\right\rceil=15$$

During dialog with characters, the player may be presented with a Speech Challenge. A Speech Challenge is a response preceded by the word "[Speech XXX%]", 'XXX' being the percentage chance of success (e.g. [Speech 25%]). Speech Challenges open up additional possibilities in dialog with characters, such as getting them to reveal information they would otherwise keep hidden or pay larger sums of bottle caps for a task. Not every Speech Challenge will have the same chance of success, since some characters may be harder to persuade than others. If failed, a Speech Challenge cannot be repeated.

The percentage of success is determined by various factors. The primary factor is the player's Speech skill. The higher it is, the better the chance of success. Charisma itself has an effect on the percentage of success. A character with a 1 in Charisma and 100 in Speech will be less effective than one with a 10 in Charisma and a similar Speech level. Having a weapon drawn will have a slight effect on the possibility of success. Finally, succeeding in a Speech Challenge with a character will make future Speech Challenges with that character easier to pass, if applicable.

Certain Speech challenges are not checked against the Speech skill, but against other factors. These can include the player's S.P.E.C.I.A.L. statistics, certain perks (Lady Killer/Black Widow, Child at Heart, etc.), or Karma. In these cases, "[Speech]" will be replaced with the relevant item being checked against ([Strength], [Karma], [Toughness], etc.). Such checks will occasionally override normal Speech Challenges. Note that these options, unlike a Speech check, will automatically succeed. Karma is an exception, as being evil or good will influence the response.

Speech success chance
The precise chance of success appears to be Charisma Bonus * Speech Skill / Difficulty, where "difficulty" depends on the particular Speech Check, but not on game difficulty level. Charisma gives a non-linear bonus according to this table:

Sample difficulties for early Speech Checks are 215 to convince Lucas Simms to increase the reward, 147 to convince Gob to give information, and 111 to convince Jericho to talk to the player. Thus a 5 Charisma, 50 Speech character has a 66 base ability, and has a 31%, 45%, and 60% chance with these checks respectively. Having a weapon raised increases the difficulty by about 10%, so with a weapon up the chances would be 28%, 41%, and 54%.

Lucas Simms is actually a fairly hard sell; few Speech Checks are harder than about 170. The hardest Speech Check in the game involves the AntAgonizer or Mechanist, and is about 457.

Strategy
In addition to counting towards the Silver-Tongued Devil achievement, successful Speech Challenges in Fallout 3 can yield the player any number of benefits though experience is always rewarded for a successful Speech check and is influenced by Well Rested status and the Swift Learner perk. Other rewards may include: a significant increase in caps for completing quests, keys or passwords, Karma, additional items, or even the chance to peacefully resolve some quests without the need for violence.

Unlike Barter (which will affect a great many transactions in the game), Speech skill will only affect specific dialogue options for the non-player character's that present speech challenges in the game. Putting a large number of skill points into Speech, or selecting it as a Tag skill assures that your character will be very, very adept with a fairly uncommon occurrence in the game mechanics.

With Speech challenges, you only have one chance. Since even a high Speech skill will not guarantee success on harder speech challenges (it will guarantee it on easier challenges, however, as long as 100% is displayed), if you're serious about succeeding in a Speech challenge, you're probably going to be careful enough to save the game before rolling the dice anyway. Using this strategy, a higher Speech skill will only increase your probability of success, which translates to fewer game reloads until you succeed. Considering this, spending ten points to increase from a Speech of 30 to a Speech of 40 is likely to be completely unnoticeable in actual practice.

It is not difficult to save the game right before initiating dialogue with most non-player characters in the game. In circumstances where a non-player character will initiate conversations with you that can include speech challenges (such as Bryan Wilks, Lug-Nut, or Goalie Ledoux), these non-player characters will only appear under predictable circumstances (nearing Grayditch, obtaining the naughty nightwear, or arriving at the Red Racer factory); thus, saving the game just before encountering these non-player characters will allow you to use the same strategy listed above. For non-player characters who can present multiple Speech Challenges—such as Bryan Wilks or Vance—it is possible to choose the option to stop speaking to them after succeeding in the first Speech Challenge, save the game, and then talk to them again to attempt the second Speech Challenge.

Ways to increase Speech
Note: Only items adding +5 or more are included.
 * Permanent
 * Leveling up (10+INT (+3 with Educated perk))
 * Bobblehead - Speech (+10)
 * Lying, Congressional Style (+1 or +2 with Comprehension)
 * Paradise Lost (+1 or +2 with Comprehension)
 * Survival Expert (+2, 4 or 6)
 * Scoundrel (+5 with each rank)
 * Tag! (+15)
 * Yew's bear charm (+10)
 * Temporary
 * Impartial Mediation (+30 with neutral Karma)
 * Ant queen pheromones (+2-6 depending on current Charisma, a perfect Charisma of 10 will see no benefit.)
 * Grape Mentats (+2-10 depending on current Charisma, a perfect Charisma of 10 will see no benefit.)
 * Pre-War businesswear (+5, includes "Dirty" and "Grimy")
 * Naughty nightwear (+10)
 * Button's wig (+10)
 * Lincoln's hat (+5)
 * General Chase's overcoat (+5)
 * Paulson's outfit (+5)