if "1 kg of grapes yields usually between 0.4 and 0.8 l of wine. For a small and semi-professional winery, such as yours, yields are rather below average."
shouldn't the calculation takes maybe 0.3 l per 1 kg of grapes the small winery yields below average?
That's a great instinct. When you encounter vague but constrained ranges like this in a case interview, the interviewer is testing your ability to set defensible assumptions and manage uncertainty.
Here’s the reality of how these estimates work in a live setting: the 0.4 L/kg floor is the key anchor. Since the prompt specifies the winery is "rather below average," selecting a number that dips beneath the stated industry minimum is the most logical choice. Your proposal of 0.3 L/kg is perfectly defensible because it explicitly fulfills the "below average" constraint, particularly by pushing past the lower limit of the standard range (0.4 L).
The critical move here is not the number itself, but how you state it. When you use 0.3 L/kg, simply tell the interviewer, "Given the prompt states the yield is rather below average, and the typical range starts at 0.4 L/kg, I will assume a yield of 0.3 L per kg of grapes to reflect their specific operational challenges." This demonstrates that you structured your choice logically around the provided constraints.
If the interviewer hasn't specifically provided a number, choose the structured lower estimate (like your 0.3 L/kg), justify it quickly, and move on. Don't waste time debating the perfect number—save the alternative figures (like 0.4 L/kg) for a quick sensitivity check later in the analysis.
Hope it helps!
