Random and systematic errors?

[Dream Capsule]

Hey guys,

 

So I did a practical about the effect of carbon dioxide concentration on photosynthesis, and we removed the gas from leaves so that they sunk in water. We then placed the leaf samples in solutions with varying sodium hydrogen carbonate concentrations, with light source coming from beneath from an overhead projector and measured the time it took for the leaves to rise to the surface of the solution.

 

So there was an uneven distribution of light across the overhead projector. Would this be a random error or systematic error? And why?

 

Thanks a lot. <3

[Schrödinger's hat]

If it's a consistent effect, that will be reproduced over all your measurements (or will change in a predictable (or even just biased) way over all your measurements) it's a systematic error.

An example would be using a ruler which was mis-calibrated so that every milimeter on it was actually 1.01mm, and thus the whole ruler would be 1.01m rather than 1m.

So if the light varied over space, and different samples were in the same spot between measurements, that would be a systematic error.

A random error is one that is un-predictable, and will change each of your measurements independantly. in the ruler example, this would be the error due to not quite holding the ruler in the right place, or mis-reading it slightly.

If the light was flickering or fluctuating between measurements (and not doing something like slowly getting brighter) then this would be a random error.