7A investigate pressure

7A have been working on pressure and as a final investigation looked at the conditions that made water rockets go furthest.
Having predicted three key variables that might make the most difference they split into groups each testing one of these independent variables; amount of water in the rocket, angle of launch and size/shape of bottle. The dependent variable for all of these was the distance travelled.
You can see the testing in progress here:

7A water rockets 2018 from Brambletye on Vimeo.

After analysis of the results 7A concluded that there was one variable that made the most difference to the flight path and this was beyond their control - the wind. Why didn't Mr P choose a calm day to conduct this experiment?