A research study is conducted looking at leg length and back…

A research study is conducted looking at leg length and back pain.  The subjects selected had low back pain.  The study was looking to determine if there was a correlation between leg length and back pain.  The subjects were to rate their pain on a 10 point scale.  A tape measure was used to measure leg length.  The subjects were measured in a standing position and bony landmarks were identified to ensure consistency in measurements among the three raters. Before research began the investigator thought that if there was a difference in leg length more than ½ an inch then the reported back pain would be greater than if the leg length difference was less than ½ an inch. Which of the following terms best describes this statement in regards to the research study?