### Functions without variances?

William Volk’s 1958 *Applied Statistics for Engineers* has put into plain words how to measure associative dependence between a function and its variance. Volk did so in *Section 7.1.4* *Variance of a General Function*. He pointed out it was his only expansion into calculus! He had been awarded a Master’s degree in mathematical statistics at Rutgers University in 1951. Volk was familiar with the properties of functions and variances. He also knew how to count degrees of freedom and why!

Volk’s knowledge of the properties of variances showed that he had been inspired by Sir R A Fisher (1890-1962). Volk had pioneered the concept of degrees of freedom for small data sets to counter Pearson’s χ²-distribution for large data sets. Sir R A Fisher built a bridge not only between probability theory and a homogeneous population but also between applied statistics and finite sets of samples taken from all sorts of sampling units and sample spaces. Sir R A Fisher had given William Volk permission to include Table 7.8 in his 1958 *Applied Statistics for Engineers*.