Question

For the Price Change data, please provide a 95% confidence interval on the variance. Select one: a. 0.10 to 2.1 b. 0.47 plus or minus 0.23 c. 0.30 to 1.50 d. 0.24 to 1.37

Background Info:

Company	Price Change ($)
Aflac	0.81
Bank of Am.	-0.05
Cablevision	0.41
Diageo	1.32
Fluor Cp	2.37
Goodrich	0.3
John.&John.	1.46
Loews Cp	0.92
Nokia	0.21
SmpraEngy	0.97
Sunoco	0.52
Tyson Food	0.12

Answer 1

Confidence interval for population Variance  

s : Sample Standard deviation; s² Sample Variance

n : Sample size

Sample variance:

Company	x: Price Change ($)	x-	(x-)2
Aflac	0.81	0.03	0.0009
Bank of Am.	-0.05	-0.83	0.6889
Cablevision	0.41	-0.37	0.1369
Diageo	1.32	0.54	0.2916
Fluor Cp	2.37	1.59	2.5281
Goodrich	0.3	-0.48	0.2304
John.&John.	1.46	0.68	0.4624
Loews Cp	0.92	0.14	0.0196
Nokia	0.21	-0.57	0.3249
SmpraEngy	0.97	0.19	0.0361
Sunoco	0.52	-0.26	0.0676
Tyson Food	0.12	-0.66	0.4356
Total	9.36		5.223
: 9.36/12=	=0.78

Given
Sample Size : n	12
Sample Variance :s2	0.475
Confidence level	95%
: (100-90)/100	0.05
/2	0.025
1-/2	0.975
Degrees of freedom : n-1	11
	21.92
	3.82

For the Price Change data, 95% confidence interval on the variance

For the Price Change data, 95% confidence interval on the variance = (0.2383 , 1.3678)

For the Price Change data, 95% confidence interval on the variance = (0.24 , 1.37)

Ans : d. 0.24 to 1.37