The 'If' part of the statement is based on related facts that you know to be true. An observation is measurable information that comes to you through your senses.
The purpose of a lab report is to organize and communicate what you did in your experiment.
A good lab report explains exactly what you have done.
My results showed the trial with the greatest amplitude was trial three because the table was being hit with the most force, making the table and the pen move more than the other three trials.
The trial with the least amplitude was trial two because the table was hit with the least amount of pressure.