We still need the variances *v*_{j}. Since each error is evenly distributed in the range , the variances of the parameters are given by
. The variance of the inputs and
desired outputs can be assumed to be zero, or they can be assigned
some values if there is prior knowledge about, for example, the
equipment used to measure the values.

In order to compute the variance of the function *f*_{i}, we shall
approximate it with first order Taylor's series expansion.

(7) |

Again we can drop out the cross terms if all are mutually uncorrelated. This yields our final approximation for the variance of a function:

(8) |