The number of hours of reserve capacity of 10 randomly selected automotive batte
ID: 3200787 • Letter: T
Question
The number of hours of reserve capacity of 10 randomly selected automotive batteries is shown to the right. 1.74 1.84 1.52 1.66 1.76 1.99 1.38 1.54 1.47 2.05 Assume the sample is taken from a normally distributed population. Construct 80 % confidence intervals for (a) the population variance sigma squared and (b) the population standard deviation sigma .
(a) The confidence interval for the population variance is (___,___ ). (Round to three decimal places as needed.)
(B) The confidence interval for the population standard deviation is (___,___ ). (Round to three decimal places as needed.
Explanation / Answer
standard deviation of population = 0.1956
degrees of freedom = 9
x^2(0.9) = 4.1682 x^2(0.1) = 14.6837
=>
(10 -1) * 0.1956 /14.6387 < variance < (10-1) * 0.1956/4.1682
=>
0.1203< variance < 0.4223
b)
0.3468 < standard deviation < 0.6499