A veterinarian wants to estimate the average weight gain per month of four-month-old golden retriever pups that have been placed on a lamb and rice diet. The population consists of the weight gains per month of all four-month-old golden retriever pups that are given this particular diet. The veterinarian wants to estimate the unknown para- meter u, the average monthly weight gain for this hypothetical population. One pos- sible estimator based on sample data is the sample mean, x = Ex/n. It could be used in the form of a single number or point estimate-for instance, 1.72 kg-or you could use an interval estimate and estimate that the average weight gain will be between 1.22 and 2.22 kg.