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How can we calculate $90\%$ confidence intervals for the variance and standard deviation of the concentration of artificial food colouring in different lots of colouring, given a random sample of $12$ lots, which yielded the following concentration values?

$0.013,0.016,0.009,0.018,0.014,0.010,0.013,0.014,0.012,0.014,0.015,0.010$

What assumptions are made?

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1 Answer

If you assume that the concentration is randomly distributed with mean $\mu$ and standa deviation $\sigma$, then you can use the same method as in this example.

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