
Ttest 
The program performs Student's ttest for significantly different means. This test is applied when two distributions x and y are thought to have the same variance, but possibly different means. The test evaluates the significance of the t=(x_{0}y_{0})/SD, where x_{0} and y_{0} are mean estimates for x and y, SD is the "pooled variance". The t value follows Student's tdistribution with N_{x} + N_{y}  2 degrees of freedom, where N_{x} and N_{y} are sample sizes for x and y. The significance is the probability that t could be this large or larger just by chance, for distributions with equal means; a value of the significance smaller than, for example, 0.05 means that the observed difference is significant at 95% confidence.
File should contain table of numerical data: lines for observations (cases) columns should be separated by tabulation or userdefines symbol (; , etc); for example, if comma (,) separator is used, the file format is the same as the CSV (comma separated values) format. No missing data allowed.
This program use statistical functions from "R" free software environment for statistical computing and graphics (http://www.rproject.org).
This program requires the Rpackage to be installed on your computer.