A knowledge of basic statistics is important for the researcher.
ChiSquare: A common analysis needed by the researcher is the comparison of two groups of data where the results can be categorized into only a few types of results. For example: Comparing the results of two different techniques of closing a tympanic membrane perforation. The results can be categorized into two types: Perforation closed or perforation not closed.
A ChiSquare test can be used to analyze this type of comparison:

For more about ChiSquare and a twobytwo online calculator go to
http://math.hws.edu/javamath/ryan/ChiSquare.html 
Twobytwo calculator with Fisher's Exact Test and Yates' Correction
http://www.graphpad.com/quickcalcs/contingency1.cfm 
For an online ChiSquare Calculator which uses up to nine rows and columns go to: http://www.physics.csbsju.edu/stats/contingency_
NROW_NCOLUMN_form.html 
Download a twobytwo calculator
http://escuela.med.puc.cl/recursos/recepidem/CHIsquare.xls 
Other Online ChiSquare Calculators:
http://people.ku.edu/~preacher/chisq/chisq.htm