A researcher for the EPA measured the amount of arsenic in the water near a sewage treatment plant. Over 5 days, he took n = 20 measurements (in parts per billion). His sample data is summarized in the ogive graph shown below (note that you can click on it to enlarge it). 20 15 10 hs 5 35 40 45 50 55 60 65 70 75 80 Arsenic (pob) How many measurements taken in this time frame were less than 65 ppb? ans = 16 X