Tina is conducting an investigation on bicycle helmet aerodynamics. She is trying to find out what kind of helmet causes the least amount of air resistance. She tested three different helmets, using the same rider each time. She recorded the time it took for the rider to complete one circuit on a track in the table below.
Helmet Time in Seconds
A 35
B 28
C 41
How could Tina get more reliable data for this experiment?