Most babies admitted to the NICU are premature (born before 37 weeks of pregnancy), have low birth weight (less than 5.5 pounds), or have a medical condition that requires special care.
Independent variable. An independent variable is used in statistics to predict or explain a dependent variable. For example, Age and Gender might be used as independent variables to predict the age of death or life expectancy (dependent variables). In experimental designs, the independent variables are manipulated by the researcher (e.g., different dosages of a drug).
1 The independent variable is the variable that is controlled and manipulated by the experimenter. For example, in an experiment on the impact of sleep deprivation on test performance, sleep deprivation would be the independent variable.  The dependent variable is the variable that is measured by the experimenter.