One measure of the effectiveness of cancer drugs is their ability to reduce the number of viable cancer cells in laboratory settings. In this experiment, the A549 line of malignant cells is plated onto petri dishes with various concentrations of the drug cisplatin. After 7 days of incubation, half the petri dishes at each dose are treated with a dye, and the number of viable cell colonies per 500 mm2 is determined as a response for all petri dishes (after Figure 1 of Alley, Uhl, and Lieber 1982). The dye is supposed to make the counting machinery more specific to the cancer cells.
Analyze these data for the effects of concentration and dye. What can you say about interaction?