Identify variables (things that change), and
things that remain constant.
What things change that affect the
experiment? (e.g., time, position of the
What things change that don't affect the
experiment? Why don't they matter to us?
(Possible Answer: The eye can be seen clearly
with either T1 or T2 weighting. The gray value
of the eye changes, but we are only measuring
What things need to remain constant to
accurately observe and measure the size of the
eye over time? (e.g., MRI instrument, same
To measure and compare the size of the
eyeball from one day to the next using the area
of the eye on a cross section, you must use a
slice that goes through the same part of the eye
in the same direction; the easiest and most
representative slice would be a section through
the fullest part of the eyeball from a saggital
or coronal view.