Chapter 11 Variance Ratio Test

11.1 Equal Variance Testing - Two Groups

## 'data.frame':    20 obs. of  2 variables:
##  $ Trout.250: num  508 479 545 531 559 422 547 525 420 491 ...
##  $ Trout.300: num  461 464 344 559 445 617 402 531 535 413 ...
##    Trout.250       Trout.300    
##  Min.   :420.0   Min.   :344.0  
##  1st Qu.:475.0   1st Qu.:415.2  
##  Median :509.5   Median :466.0  
##  Mean   :504.4   Mean   :471.4  
##  3rd Qu.:534.8   3rd Qu.:525.0  
##  Max.   :569.0   Max.   :617.0

  Figure 11.2: Box plot of rainbow trout weight distributions from two aquaculture pen densities (250 fish/pen and 300 fish/pen)
## 
##  F test to compare two variances
## 
## data:  Trout.250 and Trout.300
## F = 0.38583, num df = 19, denom df = 19, p-value = 0.04421
## alternative hypothesis: true ratio of variances is not equal to 1
## 95 percent confidence interval:
##  0.1527172 0.9747866
## sample estimates:
## ratio of variances 
##          0.3858324