An avid backyard “birder” tests two different bird foods to see which attracts more birds. On six randomly selected days, she hangs two identical feeders side by side and fills them with two different foods. She counts the number of birds in a 20-minute interval, once at 0800 and once at 1400. The data are given in Table 10.24. You wish to know whether one food tends to attract more birds, and whether the difference, if any, is more pronounced at one time of day than at another.

(a) Create a cell mean plot that will help you understand the effects.

(b) Analyze the data, assuming that day may have a random main effect but does not have interactions with either food or time of day.

(c) Analyze the data as if this were a repeated measures design with two withinsubject factors.

Table 10.24 Data for Practice Exercise 2. Time of day 0800 Time of day 1400 Food A Food B Food A Food B Day 1 32 28 15 10 Day 2 19 17 11 12 Day 3 22 20 15 11 Day 4 28 24 18 17 Day 5 32 29 22 20 Day 6 29 25 20 19 Mean 27.000 23.833 16.833 14.833