Question

An experiment was designed to see whether laboratory rats would, on average, eat more when confined to a crowded cage or an uncrowded one. To minimize the effect of genetic differences, two rats were chosen from each of 30 litters. One of each pair of rats was randomly assigned to a crowded cage, the other rat to an uncrowded cage. The data to be collected were the 30 differences in the amount of food consumed between the "crowded" and the "uncrowded" rat from each litter.

What is the natural null hypothesis for this experiment?

Shouldtheresearchhypothesisbedirectional?If so, which direction should be chosen?

Answer 1

Null hypothesis: μ₁ = μ₂.

Alternate hypothesis: μ₁ > μ₂.

Explanation:

The experimenter want to see whether laboratory rats would, on average, eat more when confined to a crowded cage or an uncrowded one.

(1)

The null hypothesis for this test is defined as:

H₀: The rats would, on average, not eat more when confined to a crowded cage or an uncrowded one, i.e. μ₁ = μ₂.

(2)

The alternate hypothesis will be directional. This is because the experimenter wants to determine whether the rats eat more or not.

So the alternate hypothesis is:

Hₐ: The rats would, on average, eat more when confined to a crowded cage or an uncrowded one, i.e. μ₁ > μ₂.