The positive correlation of .8769 between height and foot length is fairly strong, indicating that an individual's shoe size is pretty closely related to his or her height. This is what one would expect. I do not believe that one causes the other. Rather, they are both most likely affected by a common set of skeletal or growth genes, which would be the lurking variables in this study.

A common set of genes can't be the only variables at work here, however, because if you square the correlation, you get .7690 which means that only about 77% of the variance in shoe size is attributable to height in this sample. It was suprising to me that it wasn't higher. I assumed there would be a very tight relationship between the two, as there is between height and arm width ("wing span" in basketball). I expected that this relationship would be necessary for balance or proportion in human structure. However, from just my little sample, there were several outliers, and they clearly affected the strength of the correlation. These results indicated to me that although there is a relationship between height and foot length, it's not that predictive or tight.

Most likely there are other genes operating independently to affect foot length and height in addition to the common ones. I thought about nutrition as a possible lurking variable, but I would think that nutrition would impact both height and foot length in roughly equal proportion, meaning a person who is deprived of adequate nutrition in childhood ought to have both shorther height and shorter feet than their genetic potential would allow.