Final answer:
Comparative investigations face limitations such as the inability to manipulate all variables and ethical considerations, making it difficult to establish cause-and-effect relationships in studies such as jacket warmth for cold climates.
Step-by-step explanation:
One limitation of comparative investigations, like the study of different jackets for cold weather, is that they often cannot establish cause-and-effect relationships as experiments can. It is not practical, possible, or ethical to manipulate all variables in such studies. For instance, in studying nutrition of ancient ancestors, scientists rely on indirect evidence such as fossilized teeth since direct experimentation is not possible. Similarly, ethical considerations prevent researchers from conducting experiments that would expose people to harmful conditions, such as long-term cigarette smoking for cancer research.
Scientific advancements often involve testing hypotheses against observable evidence. An example of this is the historical experiment on scurvy by Lind, which led to the discovery of the benefits of citrus fruits. In contrast, hypotheses like 'cold fusion', which were quickly debunked, show the necessity of rigorous testing before scientific acceptance.
Researchers must also consider how environmental factors like microgravity affect astronaut nutrition, making direct comparative studies challenging due to unique conditions such as space travel. Understanding how heat transfer operates through materials, with thicker items providing more warmth, is another example of how comparative studies help in selecting appropriate clothing for extreme environments.