A biologist observes that ocean temperature decreases with increasing depth and concludes that deep sea creatures are superior animals because they can survive in harsher environmental conditions. Why is this an invalid scientific conclusion? The data was not compared among several sampling sites. The data did not specify the measurement system used. Scientific data cannot be used to make judgments of organism superiority. Scientific data cannot be used to measure temperatures that are inaccessible to humans.

While doing research it is recommendable for scientifics to follow the steps of the "Scientific method". The scientific method is used in scientific research for providing trustworthy and reliable answers about what is being investigated.

This method proposes six steps that must be followed when using it.

Observation: it consists of gathering information about the issue matter of research.
Hypothesis: The explanation that comes up after the observation step.
Experimentation: Here we check and test the hypothesis.
Theory: These are new hypothesis related to a lot of facts about what is being investigated.
Analysis: It helps to have evidence on the final conclusions.
Conclusions: It is the final answer after many test and analysis.

In the case provided, looks like the biologist stayed in step two making their hypothesis invalid and not reliable.