double-binning

When creating a histogram, the error of choosing the number of bins less than the number of distinct values, thus "double-binning" two distinct values into one bin.

S: "Man, I don't know what is wrong with my histogram. Why is there a spike at either end?"
M: "Have you checked for double-binning?"
S: "Ahhhhhhhh"

double-binning

When creating a histogram, the practice of choosing less bins than you have distinct values, thus "double-binning" (at least) two distinct values into a single bin.

S: "Man, this histogram looks odd. Why is there a spike at either end?"
M: "Are you double-binning?"
S: "Ahhhhhhhh"