Students design an experiment to find out if their height stays the same throughout the day.  Part of the focus is on getting students to design their own experiments, including determining variables; independent, dependent, and, in particular, controlled variables.  As the data is about the students, interest is usually high.  Reviewing data prompts discussions on what variables might not have been controlled, but should have been.  Also, often some students don't complete their individual data sets, which lends to a discussion about how incomplete data can skew results and what should be done with incomplete data.  The data provides a discussion spring board about the causes of the results.  In addition, since height is hereditary, the activity provides a segue into inheritable characteristics.  How tall are your parents, grandparents, aunts, uncles, cousins, etc.(CAUTION:  This unit can be difficult or sensitive, as some students may be adopted and not know anything about their birth families.  Also, confusion can occur as students may live with step-parents and think step-parents influence students' genetic make-up.)