When subject do not know if they are receiving the experiment treatment, they are said to bea.blindb.controlc.measurementd.product

Break Down the Problem

1. Identify the essential terms related to experimental designs, particularly regarding subjects' awareness of their treatment.
2. Understand the context in which subjects are referred to based on their knowledge of receiving treatment.

Relevant Concepts

1. Blind: In research, a "blind study" means that the subjects do not know which group they are in, common in experiments to eliminate bias.
2. Control: This typically refers to a group that does not receive the experimental treatment, used for comparison.
3. Measurement: This term refers to the process of using instruments or methods to assess variables in an experiment.
4. Product: This generally refers to the outcome of an experiment or study but does not pertain to subjects knowing their treatment.

Analysis and Detail

1. The term that specifically refers to subjects not knowing if they receive treatment is "blind."
2. In blind experiments, subjects are unaware of the specific treatment they receive, which helps mitigate the placebo effect and bias in the results.

Verify and Summarize

After analyzing the definitions and their relevance to the context, it is clear that the correct answer pertains to subjects being unaware of the treatments they receive.

Final Answer

The correct answer is a. blind.