The data below are the average one-way commute times (in minutes) of selected students during a summer literature class and the number of absences for those students for the term. Calculate the linear correlation coefficient.

Answer 1

Selected students means you are dealing with a sample from a population.
The best you can do with a sample is to estimate the correlation coefficient of the population, or the correlation coefficient of the sample.
See the formulas and examples from:

http://stattrek.com/statistics/correlation.aspx

http://www.vitutor.com/statistics/regression/correlation_coefficient.html