Final answer:
The number 2.25 represents a sample statistic, which is an estimation of the true but unknown average GPA of all OU students, calculated from a random sample of 275 students.
Step-by-step explanation:
The number 2.25 is an estimate of a sample statistic. In statistics, a sample statistic is a measure that is calculated from the data collected from a sample and is used to estimate a population parameter. The population parameter, in this case, is the true average GPA of all OU students, which is a fixed but unknown value. Since the professor is looking to estimate this parameter, the result from the student sample (2.25) serves as the sample statistic providing an estimate of the true population parameter.