Rabbit preference for cage with pheromone


This diagram illustrates that the p-value puts a numerical value to the scale of the type of diagram used on the previous page — it describes whether the data are consistent with the null hypothesis, H0.

The p-value is an index of credibility for the null hypothesis, µ = 0.

Also mention that the interpretation of the p-value is identical for all hypothesis tests, regardless of the details of H0 and HA.

An experiment is conducted to assess whether rabbits are influenced by a particular pheromone, either positively or negatively. A large cage is constructed whose features (water, food, etc.) are duplicated symmetrically on both sides of a centre line. A rabbit is placed in the centre of the cage and a small quantity of the pheromone is added to one side. During the next 5 hours, a technician records the number of minutes that the rabbit spends in each half of the cage. This experiment is repeated with 16 rabbits.

Do the rabbits tend to spend half their time in each side of the cage (indicating that they are unaffected by the pheromone) or do they tend to spend more time in one or other half (indicating attraction or repulsion)? We examine this question using the difference between the times in the two sides of the cage, pheromone minus non-pheromone. This question is equivalent to asking whether there is evidence that the underlying population mean of these differences could be zero. If µ = 0, the pheromone has no effect, whereas µ > 0 indicates a preference for it and µ < 0 indicates avoidance of it.