Sample Size,  n=  40 Â
Sample Standard Deviation,  s= Â
65.5000Â Â
Confidence Level,  CL= Â
0.90Â Â
       Â
       Â
Degrees of Freedom,  DF=n-1 =  Â
39Â Â
alpha,  α=1-CL=  0.1 Â
alpha/2 ,  α/2=  0.05 Â
Lower Chi-Square Value=  χ²1-α/2
=Â Â 25.6954Â Â
Upper Chi-Square Value=  χ²α/2 = Â
54.5722Â Â
       Â
confidence interval for variance is    Â
  Â
lower bound=  (n-1)s²/χ²α/2 = Â
3066.02Â Â
       Â
       Â
upper bound=  (n-1)s²/χ²1-α/2 = Â
6511.66Â Â
       Â
    Â
confidence interval for std dev is  Â
  Â
lower bound=  √(lower bound variance)= √3066.02
= 55.4
    Â
    Â
upper bound=  √(upper bound of variance= √6511.66 =
80.7
    Â