Answer: Statistic
Step-by-step explanation: The difference between a parameter and statistic lies in the set of observation from which either quantity is derived. The parameter represents numerical values which are derived by examining or considering an entire population while the statistic is used to define numerical quantities derived from subset of the population called the sample. In the scenario described above, the population of interest would be the entire population of student and hence statistical derivations made would be called parameters. However, the scenario only experimented using student from two different classes which is a subset of the entire population of student. Hence, the obtained mean values of 25.40 and 20.41 for students in the formal and informal classes are categorized as statistic.