Question

A researcher at a pharmaceutical company is interested in testing out the effects of a new drug, which he thinks will improve attention. However, he also suspects that the effects of the drug interact with caffeine. To test this, he tests six separate groups (n = 10, in each group), given either a drug, a placebo, or no drug, and either having consumed caffeine, or no caffeine. Each performs an attention task. He collects the following data.

	drug	placebo	no drug
Caffeine	x = 5	x = 10	x = 15
	x2= 210	x2 = 330	x2= 415
No Caffeine	x = 20	x = 10	x = 6
	x2= 780	x2 = 345	x2= 270

What is the F-value (F-obtained) for the interaction between drug and caffeine (AxB interaction)

Answer 1

Excel:

Data --> Data analysis --> Anova: Two-Factor With Replication

Output:

ANOVA
Source of Variation	SS	df	MS	F	P-value	F crit
Sample	16576.33	1	16576.33	0.186961	0.680567	5.987378
Columns	16500.17	2	8250.083	0.093051	0.912436	5.143253
Interaction	74965.17	2	37482.58	0.422757	0.673342	5.143253
Within	531973	6	88662.17
Total	640014.7	11

F-value (F-obtained) for the interaction = 0.422757