18. A sample of 20 cans of tomato juice showed a standard deviation of 0.4 ounces. A 95% confidence interval estimate for the variance of the population is
a. 0.2313 to 0.8533
b. 0.2224 to 0.7924
c. 0.0889 to 0.3169
d. 0.0925 to 0.3413
Solution :
Given that,
s = 0.4
Point estimate = s2 = 0.16
2R = 2/2,df = 32.852
2L = 21 - /2,df = 8.907
The 95% confidence interval for 2 is,
(n - 1)s2 / 2/2 < 2 < (n - 1)s2 / 21 - /2
(19)(0.16) / 32.852 < 2 < (19)(0.16) / 8.907
0.0925 < 2 < 0.3413
(0.0925 to 0.3413)
option d. is correct
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