Step 1: Understanding the Concept.
Pilot plant studies exist to catch scale-up problems, such as mixing, heat transfer, or compression behaviour, before a formulation is committed to full commercial manufacture.
Step 2: Key Approach.
Two things need to be correct together: the reference batch being compared to (production batch, not marketing batch) and the ratio itself (one-tenth, not one-fifth).
Step 3: Detailed Explanation.
A marketing batch refers to the commercial batch actually released to the market under approval, which is a regulatory and distribution concept rather than the technical reference used for scale-up ratios.
The production batch is the true reference, since it represents the routine full manufacturing scale that the pilot batch is meant to approximate on a smaller footprint.
Industry practice sets the pilot batch at roughly one-tenth of that production batch size, large enough to be meaningful for testing equipment behaviour, small enough to limit the cost of a failed trial.
A ratio of one-fifth would make pilot runs unnecessarily large and expensive for their purpose.
Step 4: Final Answer.
The size of a pilot plant batch is \( \frac{1}{10} \)th of the production batch.