Final answer:
The statement 'The sample size is small' is the least helpful in establishing that a conclusion is properly drawn as it indicates a potential weakness in the evidence, which can undermine the reliability of the findings.
Step-by-step explanation:
The question is asking which piece of information is least helpful in supporting the proper drawing of a conclusion when all statements are true. Among the options provided, (c) The sample size is small would be the least helpful piece of information in establishing that a conclusion is properly drawn because it signifies a potential weakness in the evidence. Scientific conclusions rely on sufficient and representative data, and small sample size can lead to less reliable or generalizable results.
In contrast, evidence based on rigorous scientific studies (a), consensus among experts (b), and a conclusion that aligns with existing knowledge (d) all strengthen the validity of a conclusion. These factors contribute to building confidence in the hypothesis being tested.