F-Distribution

The F distribution calculator makes it easy to find the cumulative probability associated with a specified f value. Or you can find the f value associated with a specified cumulative probability. What are degrees of freedom? Degrees of freedom can be described as the number of scores that are free to vary. For example, suppose your friend tossed three dice, and the total score added up to 12. If your friend told you that he rolled a 3 on the first die and a 5 on the second, then you know that the third die must be a 4 (otherwise, the total would not add up to 12). In this example, 2 die are free to vary while the third is not. Therefore, there are 2 degrees of freedom. In many situations, the degrees of freedom are equal to the number of observations minus one. Thus, if the sample size were 20, there would be 20 observations; and the degrees of freedom would be 20 minus 1 or 19. What is f-value? An f value (also known as an f statistic) is a random variable that has an F distribution. Here are the steps required to compute an f value: Select a random sample of size n1 from a normal population, having a standard deviation equal to σ1. Select an independent random sample of size n2 from a normal population, having a standard deviation equal to σ2. The f value is the ratio of s12/σ12 and s22/σ22. Thus, f = [ s12/σ12 ] / [ s22/σ22]