A study is commissioned to determine whether piglets gain body mass more rapidly when a certain hormone is introduced into their feed. In January, a random sample of 40 10-week-old piglets receives a diet that includes the hormone. Sixteen weeks later, the average weight increase is determined. A similar experiment is conducted the following June with a random sample of 36 piglets, except the hormone is removed from the diet.
Which of the following do you think represents the most serious flaw in this study?

A)the presence of a confounding variable
B)the presence of a sampling bias
C)an absence of experimental control
D)the presence of a measurement bias
E)inadequate information regarding dietary needs of piglets

Question

A study is commissioned to determine whether piglets gain body mass more rapidly when a certain hormone is introduced into their feed. In January, a random sample of 40 10-week-old piglets receives a diet that includes the hormone. Sixteen weeks later, the average weight increase is determined. A similar experiment is conducted the following June with a random sample of 36 piglets, except the hormone is removed from the diet. ​
Which of the following do you think represents the most serious flaw in this study?
​
A)the presence of a confounding variable
B)the presence of a sampling bias
C)an absence of experimental control
D)the presence of a measurement bias
E)inadequate information regarding dietary needs of piglets

Quizplus · Accepted Answer

The study has a confounding variable, which is the time of year (January vs. June) when the experiments were conducted. Seasonal variations could affect piglet growth independently of the hormone, thus confounding the results.

A Study Is Commissioned to Determine Whether Piglets Gain Body