# Impact Factors

I tear my hair out over the widespread habit of listing a journal’s Impact Factor to four digits of precision. Today I attended a journal editorial board meeting in which we were let inside the sausage factory:

Citations in 2 years/no. of papers = $\displaystyle{350\over 146}$ = 2.397.

Abracadabra! Three digits in, four digits out!

But the true problem is larger. With a three-digit sample size, the square-root effect of statistics tells us we should trust the quotient to about 1.5 digits. Not 3. Certainly not 4 — that would require a sample size of 108. This 4-digit Impact Factor is 62.5% garbage.

[4 September 2020]