You are conducting a study on the preferences of female sage-grouse for large th

Question

You are conducting a study on the preferences of female sage-grouse for large throat sacs on males (see picture), where larger inflatable sacs may signal better body condition and better genes. You already know that females prefer males with larger sacs. You create a set of five male robotic sage-grouse that appear and behave identically (they are robots and can hop around in a circle and vocalize like normal males) but only vary in the size of their throat sacs: very small, small, intermediate, large, and extra large. You also have a female model to use as a control.  You present these models to 40 temporarily captive females in the field that are ready to mate. You test the females, one at a time, in a fenced off experimental area where no other birds (male or female) are visible. For each female, you show them the models one at a time, in this order: female, very small sacs, small sacs, intermediate sacs, large sacs, and extra large sacs, and then observe which model they approached most rapidly and spent the most time with, indicating a greater preference. You discover that out of the 40 females, 33 preferred the males with the extra large sacs, 6 preferred the male with large sacs, and 1 preferred the intermediate male. This is very strong evidence supporting your hypothesis that holds up after statistical testing: females definitely prefer males with larger throat sacs. You write up your results into a scientific paper to get them published but the reviewers reject your paper, saying there was a fatal flaw in your study design.  What was the problem with your study, why is it a problem, and what should you have done instead. (4 points)

Explanation / Answer

The male sage-grouse used were robotic in nature. Hence though females get attracted towards the larger throat sacs of robotic males, they may not spent most time with males. Rather they could have used real males having different characteristics of throat sacs.

Secondly, female can not be used as a control in the study design. Males having different sizes of throat sacs would have been the test groups.

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