Answer:
8.3 < σ < 16.2
Step-by-step explanation:
The population variation can be estimated between:
(n−1) s² / χ²α/2 < σ² < (n−1) s² / χ²(1−α/2)
At 90% confidence and 13 degrees of freedom, χ²α/2 = 22.4 and χ²(1−α/2) = 5.89.
(14−1) 10.9² / 22.4 < σ² < (14−1) 10.9² / 5.89
69.0 < σ² < 262.2
8.3 < σ < 16.2