= Solution
\b[First agree the scientific question and primary <response variable>.] Ask the vet about the disease's course, the proposed mechanism and duration of each treatment, the eligible population, baseline severity, and what outcome and follow-up time would represent worthwhile improvement. Is the disease transmissible, is recovery reversible, and can treating one cow affect another's outcome? These answers determine whether a <crossover design> is credible, whether the <experimental unit> should be a cow or a whole herd, and whether individual <randomization> would leave interference between groups. Agree welfare and rescue arrangements with the vet when deciding which comparisons are feasible; the statistical plan cannot determine these from an unfamiliar disease name.
\b[Second agree feasible allocation and adequate independent <replication>.] Discuss numbers of available cows and herds, variation in the chosen outcome, a scientifically meaningful treatment difference, and the desired <statistical power>. Use these to plan <sample size>, rather than choosing a number solely from convenience. Discuss herd, lactation stage and initial severity as potential <blocks in experimental design>, then specify <randomization>, comparable management, concealed allocation and blinded outcome assessment where feasible. Repeated milk or health records from the same cow are <observational units>, not extra independent <experimental units>; <pseudoreplication> would give misleading <standard errors>. Availability of enough independent cows or herds, together with expected variation, governs the precision actually achievable.
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