The following data was taken from the sludge of the waste treatment plants in two cities. The data represents levels of Zinc in ppm in the sludge. Both cities used identical equipment in their treatment plants, and the data were collected during the same time periods. City A 25.2 39.2 25.5 31.9 City B 47.7 39.1 55.3 50.7 2.1. First, calculate a separate 95% CI for the mean Zinc in each city (to be clear, you're making two separate confidence intervals. Show your results. 2.2. These two intervals overlap. What might this suggest about zinc levels between cities? 2.3. Now, find a single 95% CI for the mean difference between groups. You may want to use 'Each sample is in its own column' if you have the data for each city in a different column. Perform a two-sided hypothesis test. What do you conclude? 2.4. The results of 2.1 and 2.3 might seem contradictory. Which method is correct: doing a single two-sample confidence interval comparing means, or doing two separate on-sample intervals and seeing if they overlap? 2.5. Repeat part 2.3, but now assume equal variances. Compare results between assuming or not assuming equal variances. Do you feel justified in using the 'equal variance' test?