As part of a follow-up study, a researcher decided to investigate the effect that dosage of a drug (none, low dose, medium dose, high dose) and difficulty (easy, moderate, difficult) of a maze have on the number of attempts it takes for rats to complete the maze with no errors. They randomly assign the rats to the various treatment combinations and have them run the maze repeatedly until they complete it successfully. The results can be found in the file homework 4 maze. a) Identify the explanatory and response variables. For each, determine if they are categorical or quantitative. How many treatment combinations are there? How many rats are there per treatment combination