Analysis

The weight, the speed in which you pull the spring scale, and the surface material. The relationship between weight and speed in which you pull the spring scale is is non-existent. The relationship between the weight and the surface material exists, because the weight cannot be to little or to less. If its to small, secure contact between the shoe and the surface is not reliable. If its to heavy, the shoes sole may deform. If its really heavy, than the surface may deform,too. The relationship between the speed and the surface does not exist. We can improve the experiment by changing weight and the surface material, such as doing it outside compared to doing it on the carpet.