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eText Book Here! 20 × M8 Assignment ©EText Book Here! 20 × ©Chegg Study! Guid × 90 confidence inter × . Untitled document × © ETet Book Here! 20X + wwww.webassign.net/web/Student/Assignment-Responses/submit?d 90% … |Q.Search 30. 8 points BBUnderStat1 274.012 My Notes Ask Your + Inorganic phosphorous is a naturally occurring element in all plants and animals, with concentrations increasing progressively up the food chain (fruit vegetables cereals nutscorpse). Geochemical surveys take soil samples to determine phosphorous content (in ppm, parts per million). A high phosphorous content may or may not indicate an ancient burial site, food storage site, or even a garbage dump. Independent random samples from two regions gave the following phosphorous measurements (in ppm). Assume the distribution of phosphorous is mound-shaped and symmetric for these two regions Region 1: x1,n1 = 15 855 1550 1230 875 1080 2330 1850 1860 2340 1080 910 1130 1450 1260 101 Region 11: X2; n2 = 14 540 810 790 1230 1770 960 1650 860 890 640 1180 1160 1050 1020 (a) Use a calculator with mean and standard deviation keys to verify that X1, S1, X2, and s2. (Round your answers to one decimal place.) X1- ppm ppm ppm ppm (b) Let be the p lower limit upper limit n mean for X1 and letK2 be the population mean for X2. Find a 90% confidence interval for 1-12, (Round your answers to one decimal place.) ppm ppm (c) Explain what the confidence interval means in the context of this problem. Does the interval consist of numbers that are all positive? all negative? of different signs? At the 90% level of confidence, is one region more interesting than the other from a geochemical perspective? 0 Because the interval contains both positive and negative numbers, we can not say that one region is more interesting than the other. O Because the interval contains only positive numbers, we can say that region I is more interesting than region II. O Because the interval contains only negative numbers, we can say that region II is more interesting than regionI. O We can not make any concdusions using this confidence interval. (d) Which distribution (standard normal or Student's t) did you use? Why? 4:31 PM O Type here to search 11/20/2017Explanation / Answer
a)
Descriptive Statistics: Region 1, Region 2
Total
Variable Count Mean StDev
Region 1 15 1387 498
Region 2 14 1039.3 346.7
b) 90% Confidence interval: 74.61681 < µ1-µ2 < 621.4784
c) Correct Answer: Option (B)
d) Student's t was used because sigma1 and sima2 are not known
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