3. For the following scenarios, identify whether you should use z or t in a confidence interval calculation. (You don't have to do anything else.) (Scenario 1) Mickey is interested in the average amount of water a broom carrying water buckets could pour into a cistern. It is believed that the amount of water carried is approximately normal. A random sample of 28 water buckets was taken and it was found that, on average, each bucket could hold 4.8 gallons of water, with a standard deviation of 0.2 gallons. A 92% confidence interval was created. (Scenario 2) Minnie owns a boutique that sells hair-bows and bow-ties. On a normal day, Minnie makes many sales. The average selling price is approximately normally distributed with a standard deviation of $0.72. Minnie is interested in the average selling price of products sold on one day. A sample of 36 sales were investigated from that day, and it was found that the average selling price was $4.78. A 93% confidence interval was created. 4. Arsenic concentration in public drinking water supplies is a potential risk. Drinking water arsenic concentration (ppb) for various metropolitan rivers were tested. Measurements were taken either at a drinking water facility upstream of the metro area, or at a drinking water facility downsteam of the metro area. Upstream Metro-Area 13 1 2 3 7 4 5 6 25 10 15 6 40 38 33 21 7 8 12 25 20 12 1 9 10 15 7 18 Downstream 48 44 Goal: Find a 98.17% confidence interval. Procedure: We carried out the analysis in R. Below is the output for 3 different ways the data could be analyzed. Potential R Output: upstream t.test(upstream, downstream, alternative = "two.sided", var.equal = TRUE, conf.level = 0.9817)