I am unsure about an expression in Stone's (1997) paper on asymptotic equivalence between AIC and LOOCV. Section 4., third line from the bottom of page 45 starts with $L(\theta)-1(y_i|x_i,\theta)$. The second part of this expression is puzzling to me.
What does $1$ stand for? An indicator function?
Or should it actually be $l$ rather than $1$, meaning the likelihood of a single observation $l(y_i|x_i,\theta)$?
- Stone, M. (1977). An asymptotic equivalence of choice of model by cross‐validation and Akaike's criterion. Journal of the Royal Statistical Society: Series B (Methodological), 39(1), 44-47.