Random errors

Random errors are errors made by the person carrying out the measuring, and are usually down to timing incorrectly, or reading the instrument incorrectly. It is important to try to reduce or limit the effect of random errors in measuring.

Reaction time errors and parallax errors are examples of random errors.

A surface is at 45 degrees to a table. At the top is a vehicle with a piece of card attached. At the bottom is a light gate attached to a laptop.Reaction time error can sometimes be reduced by using light gates and electronic timing or sensors connected to a computer to record time taken for objects like paper cake cases to fall or a vehicle to move down a slope

Parallax error

3 sets of eyes reading a measurement on a ruler. The 2 sets of eyes above and below the eye level are marked with a cross. The set of eyes in line with the correct measurement is marked with a tick.

Parallax error is caused by a student not reading the measurement at eye level. It can lead to the reading being too high or too low.

Systematic errors (zero errors)

Zero errors are caused by faulty equipment that doesn’t reset to zero properly.

Check before you start measuring that the measuring instruments read zero for zero input.

A zero error would affect every reading you take. The digital balance will be wrong by 0.02 g on every mass you measure and the force meter would be wrong by 1 N.