A scientist who works in animal physiology wants to study perception of uv light in rats. she randomly selects 20 rats and records how far each rat travels in 5 minutes inside a dark maze. the distance is recorded and then the rats are returned to the starting position. the maze is then "illuminated" with uv light and the rats are again given 5 minutes to travel through the maze. this distance is then recorded. which hypothesis test would be most appropriate for this study?