anchor.diff:  // sample properties are given as (variance,degree of freedom) 
   let sampleF1 = (0.1, 15.)
   let sampleF2 = (0.05, 7.)
  +
   // comparison of sample variances 
   let fTestFromParameters = FTest.testVariancesFromVarAndDof sampleF1 sampleF2
   (*
  
positive.code: (**
  <a name = "FTest"></a>
  ##F-Test
  The F-test is a method to determine if the variances of two samples are homogeneous. 
  Also, ANOVA (analysis of variance) is based on the F-test and is used for the comparison of more than two samples.  
  ANOVA can detect if there is a difference in variances between samples, without pre-specifying which samples should be compared. 
  Knowing if your variances are equal (H<sub>0</sub> is true) helps to decide which test should be done next. 
  To determine if your variances are in fact equal you can perform a F-test. 
  
  Prerequisite : 
  
    -   samples are normally distributed 
  
    -   samples are independent
  
  Possible further tests :
  
    -   two sample t-test with equal variances
  
  
negative.code:     DegreesOfFreedom1 = 15.0
      DegreesOfFreedom2 = 7.0
      PValue = 0.17963663 }
      Using a significance level of 0.05 the sample variances do differ significantly.
  *)
  
  
  