Bias

When there is a target, a value's bias is its difference from the target.

Root mean squared error

One solution to the problem of negative errors cancelling positive ones is to square them before averaging. For the weights of the bags of potatoes, this would give a value whose units are 'squared kg', so we use its square root to summarise the size of the errors,

root mean squared error   =   

The root mean squared error is a 'typical' error.


Weights of 3kg bags of potatoes