A knowledge of basic statistics is important for the researcher.

Paired T-Test :  

This test is used to compare two different groups of data where the observations cannot be categorized into a few defined categories.  (It is used to compare two different populations of data).  . 

Links to calculate T-Tests online:

• T-Test Calculator.  These sites allow you to enter individual observations into two groups and perform a T test. 
  http://www.graphpad.com/quickcalcs/ttest1.cfm  
  http://www.changbioscience.com/stat/ttest.html 

• T-Test Calculator.  These calculators allow you to perform T-Tests by entering the mean, number of observations and the standard deviation of the two groups.
  http://www.quantitativeskills.com/sisa/statistics/t-test.htm   
  http://www.dimensionresearch.com/resources/calculators/ttest.html 
  http://glass.ed.asu.edu/stats/analysis/t2test.html