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lab6f09_ans - Stat 401C Problem 1 Lab#6 Solution Key Fall...

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Stat 401C Lab#6 Solution Key Fall 2009 Problem 1 a) The normal probability plot ( see attached JMP output ) shows that the points fall approximately on a straight line supporting the assumption that the paired differences of PCB measurements at the sites is a sample from a normal distribution. The box plot also supports this conclusion. See the attached Excel output for the calculation of d s and d s . b) Let 1996 1982 µ µ µ = d where 1982 µ and 1996 µ are assumed to be the means of PCB contents in gull egg populations during those years. Assuming that the paired differences in PCB content is a sample from normal population with mean d µ the following hypotheses can be tested: 0 : 0 d H µ vs. 0 : > d a H µ d c s d t 0 = = 23 . 11 13 / 46 . 12 80 . 38 = 681 . 2 12 , 01 . = t , that is R.R. is 681 . 2 > t Since c t is in R.R. we rewject the null hypothesis at 01 . = α and conclude that there has been a significant decrease in mean PCB content in the herring gull egg population.
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