Question 1:
Sample is some selected subset of the entire student body of University of Colorado.
When only some subset of student of University Colorado is taken, then we say that we consider a sample.
Under the condition that subset of University of Colorado students is selected.
Another way to answer:
Entire student body of the university is considered sample if it is a subset taken from population which is all people of University of Colorado Denver (student, teachers, administration).
When students of University Colorado are taken as a subset of students and faculty altogether, then we say that we consider a sample.
Under the condition that student body of University of Colorado is selected as a subset from the population which comprises faculty, students, and administration of the university.
Question 2:
Entire student body of University of Colorado is considered a population.
If all students of student body of University of Colorado are selected, then we say that we consider a population.
Under the condition that all students of University of Colorado are selected.
Question 3:
Mean calculation takes every value of the distribution; therefore, it is influenced more by outliers, while median is the middle value of the distribution.
Mean is more affected by outliers as it is a value which is produced by combining all of the values of the distribution together.
Effect of outliers on mean statistic is more dramatic than on median because mean considers each member of the distribution.
Reference
Please cite your book here, I do not have an access to its full version.
