Problem description

27 chicks from a single hen are placed in a cage with two adjacent cages. One cage always has one of mom, unrelated female, and male treatments while the other cage is empty. Each chick sees all 3 treatments in one of three orders:

  1. mom, unrelated female, male
  2. unrelated female, male, mom
  3. male, mom, unrelated female

with the first treatment always placed in the “right” cage. For each chick-treatment combination, whether or not the chick “follows” (goes toward) the treatment is recorded. If a chick follows the first treatment, the second treatment is placed in the left cage.

Client question(s)

  • Do chicks follow mom more often than other treatments?
  • Does order of treatments matter?
  • Do chicks act differently the more times they have done the experiment?
  • Does this depend on chick gender?
  • Does cage direction matter?

Consulting response

A real concern is the change of treatment location depending on the previous response. This is a sequential design and difficult to analyze.

Another concern is that not all orderings of treatment are present, e.g. unrelated female, mom, and male. Thus, there will be some confounding between treatment and order.

There are a lot of explanatory variables in this model that may affect the response. Thus a much larger sample size is suggested.

Finally, since a single mother is used the results are not generalizable to any larger population.

Thus, this should only be used as a pilot study and a better design should be used in the future.

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29 November 2018