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A quality control check on the batch production of wooden skewers involves sampling and measuring the average length of the skewers per batch.
For Batch A, a random sample of 20 skewers were found to have an average length of 21.6 cm.
For Batch B, 10 random skewers gave an average length of 20.4 cm.
The standard error in the difference was found to be 0.766 cm.
Calculate the 99% Confidence interval on the difference in length between the two batches (A-B).
Assume that the lengths are normally distributed, do not assume the population variances are equal, and use the conservative "by hand" estimate for the degrees of freedom (ie lesser n-1).