What is the source of my speed error in my steel ball experiment?

[THE 1]

Basically i am working out my error
i did an experiment where i dropped steel balls through glycerol and started the stopwatch at a line and stopped it at a line. The lines are displaced 40cm or 0.4m apart form each other. If a humans reaction time is approximatly 0.3s then my error in speed is 0.3x2/0.4=1.5m/s but this is a massive error as my spheres were moving at less than 1m/s so I am a little confused that my error can be this much.

Help Needed

 

[DaveC426913]

Do you want help with the math, or with the experiment?

There must be a more reliable way than your reflexes for timing the events.

 

[tyco05]

I remember doing this experiment a long time ago... and yeah, the way that we did it relied on our reflexes to time the events.
How many balls of the same diameter did you drop? If you did a plentiful amount, you could do a statistical error analysis?