Question

The weights of a random sample of jam jars that are supposed to weigh 100 grams are listed below: The data are listed below: 105.2 103.5 98.6 100.3 99.1 97.8 101.2 96.0 The sample statistics are: ?̅= 100.213, ? = 3.025 Estimate the variance of the entire population of jam jar weights with 95% confidence. How would I use excel to solve this?

Answer 1

	here n =	8
	s2=	9.151
Critical value of chi square distribution for n-1=7 df and 95 % CI
Lower critical value χ2L=		1.690
Upper critical valueχ2U=		16.013

for Confidence interval of Variance:
Lower bound =(n-1)s2/χ2U=		4.000
Upper bound =(n-1)s2/χ2L=		37.905
from above 95% confidence interval for population variance =(4<σ2<37.905)

from excel use below formula :

lower bound =(8-1)*(3.025)^2/chiinv(0.025,7)=4.000

upper bound =(8-1)*(3.025)^2/chiinv(0.975,7)=37.905