Klok, Hubb, and Harrison (2009) hypothesized that the difference in insect size was due to the higher atmospheric oxygen concentration during the late Palaeozoic, compared to today. They did this experiment to test this hypothesis. From a population of fruit flies, they separated them into the following conditions: current atmospheric conditions, and hyperoxic atmospheric conditions. All other conditions were identical. After 8 generations, they weighed the fruit flies from each condition. Required:
a. Which is the independent variable(s) and which is the dependent variable(s), if any?
b. Are the variables discrete, continuous, categorical, or ordinal?
c. What type of graph would you use to describe these data? How would you label the x and y axes?