Using the Hat Matrix Elements Hi to Determine Influential Points $h _ { i } < 2 ( k + 1 ) / n$

Short Answer

Using the hat matrix elements hi to determine influential points in a multiple regression model with k independent variable and n observations, Xi is an influential point if a) $h _ { i } < 2 ( k + 1 ) / n$
b) $h _ { i } > 2 ( k + 1 ) / n$
c) $h _ { i } < n ( k + 1 ) / 2$
d) $h _ { i } > n ( k + 1 ) / 2$