A supplied counting model

For a fictional manual leukocyte count, twenty microlitres of blood are mixed with 380 microlitres of the assigned diluent. The laboratory counts 160 cells in four squares whose combined counted volume is 0.4 cubic millimetres. The chamber, technique and sample are assumed suitable for this calculation. A trainee divides the count only by four and reports that number as cells per litre. No actual patient decision is attached to this exercise. The supervisor asks for the dilution factor, the volume correction and the final unit conversion, then asks why a mathematically correct answer would still not establish the reliability of a poorly mixed or partially clotted sample.