Nothing – Fisher chose the letter “t” just as a simple way to refer to Gosset’s Student distribution.
“In his 1908 paper, “The Probable Error of a Mean”, Biometrika, 6, 1-25 Gosset introduced the statistic, z, for testing hypotheses on the mean of the normal distribution. Gosset used the divisor n, not the modern (n – 1), when he estimated and his z is proportional to the modern t with t = z sqrt (n – 1). Fisher introduced the t form because it fitted in with his theory of degrees of freedom (q.v.). Fisher used the t symbol and described Student’s distribution (and others based on the normal distribution) and the role of degrees of freedom in “On a Distribution Yielding the Error Functions of Several well Known Statistics”, Proceedings of the International Congress of Mathematics, Toronto, 2, 805-813. Although the paper was presented in 1924, it was not published until 1928 (Tankard, page 103; David, 1995). According to the OED2, the letter t was chosen arbitrarily. A new symbol suited Fisher for he was already using z for a statistic of his own (see entry for F).”
I’m not trying to be rude but I would like to ask you why you keep bumping your post to the top of the list? If you are hoping for a different answer I’m afraid you won’t get one. The answer I provided is a direct quote from a history text.
@rbutler – That’s me. I changed the title once and then recategorized the discussion so it wasn’t in “Welcome.” Sorry for the confusion.
Ok, thanks Katie – sorry about that Dan