BHS -> Mr. Stanbrough -> Physics -> About Science -> this page
To answer the question posed by the experiment, a physicist must set up a situation (apparatus) and collect data (make observations). It is always important that an experiment's equipment and procedures are carefully documented, so that its results are reproducible - scientific observations must be repeatable.
Once the data (observations) are taken, physicists then process and summarize this data in order to draw some conclusions (answer the original question, if possible).