statistics
posted by Anonymous .
The data below are the average oneway 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.

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