F statistics test for equality of variances

-------

curve 

f()= Gamma[(n1+n2)/2] * (n1/n2)^(n1/2) / [ Gamma(n1/2)*Gamma(n2/2) ] *



Integral {f to oo) x^(n1/2-1) / (1+ n1/n2*x)^(( n1+n2)/2 ) dx



n1= Degrees of freedom for greater mean square

n2= Degrees of freedom for lesser mean square



Value is area under curve from F to infinity

============================================

Example n1=4   n2=3   

x nalue   9.12

Num df:   4

Num df:   3   Enter



results= 0.007353724852



TI-89 F5 Distr   9:F Pdf gives value of y function

 

====

Find area under curve from f=x=9.12 to 1000

A: F Cdf

---

Lower Value   9.12

upper Value   1000

Num df        4

Denom df      3



area = 0.049928003672 



Shape of curve



|   /\

|  /  \

| /    \____

______________