Programmers can make the variables easy to understand by choosing meaningful names. 
However, even though individual names are meaningful, a collection of them might adversely 
affect the code readability when their names are highly similar, such as bottomRight vs. bottomHeight, 
and they may cause mixing up or misreading of variables. 
Such a pair is referred to as a confusing variable pair. 
This paper conducts a large-scale investigation to examine the change trends of confusing variable pairs over commits, 
and it reports the following findings. 
(1) The average number of confusing variable pairs appearing in a source file is 1.4 in Java and 1.3 in Python. 
(2) About 67–75% of confusing variable pairs survive through commits. 
(3) Confusing variable pairs tend to appear in a subset of source files within a project (the median rates in Java and 
Python projects: 26% and 13%) and disappear from fewer files (the median rates in Java and Python projects: 6% and 2%). 
(4) Although the change trends do not vary among projects, some outlier projects have significantly more confusing variable pairs.