title: the argument `var.equal=TRUE or FALSE` in 't.test()' function
body: <p>When will I use the argument <code>var.equal=TRUE</code> or  <code>var.equal=FALSE</code> ?</p>
  
  <p>i haven't understood by reading the r documentation file.</p>
  
  <p>Could you give me practical example to make it clear to me the situation of var.equal=TRUE or FALSE? </p>