Variable expenses, like gas or groceries, are costs that vary due to price or consumption changes. Fixed expenses, like your rent or mortgage, usually stay the same.

Scientists often want to find out if changing one variable makes a difference to other variables. In many (though not all) investigations the variables are kept constant - the control variables ...

Sorting by CONTROL variables is available for systematic and sequential selection methods, which include METHOD=SYS, METHOD=PPS_SYS, METHOD=SEQ, and METHOD=PPS_SEQ. Sorting provides additional control ...

Two rules are developed for determining control variables when studying respectively the direct and the total effects of a cause on an outcome. An application to contraceptive use in urban Africa is ...

Then an example of variable selection with four response variables and two methods is given and we conclude by making some recommendations for their routine use. The Statistician joined the Journal of ...