C-type batteries have a nominal diameter of 26.2 mm. Producing batteries with this value will ensure they fit properly into all toys and appliances that require C-type batteries. A tolerance variation of 0.000225 mm² (? = 0.015 mm) is allowable. After repair, a machine produces a batch of 12 C-type batteries with the following diameters in mm.

(a) Construct a 95% confidence interval for ?².

(b) Does this variation appear acceptable?

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26.19 26.20 26.21 26.19 26.18 26.18 26.24 26.22 26.16 26.20 26.21