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# Lab7 - STAT 350 Lab#7 2-way ANOVA Due Friday April 4 2008...

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STAT 350 Lab #7 – 2-way ANOVA Due Friday, April 4, 2008 at the beginning of class For the following problems, do the analysis using SAS. Please put all SAS input (Editor window) and all SAS output (Output window, NOT the Log window) as an appendix. Nothing pasted directly from SAS should be given as an answer to the questions below! The Experiment A wood scientist (yes, there are such people. .. even right here at Purdue) has come to you for help analyzing an experiment. He had wanted to examine the durability of wood used for decking. Deterioration of wood in use is commonly caused by decay fungi, certain insects (including termites) as well as other organisms, and weathering. He wanted to examine various species of wood and various preservatives. He used 3 species of hardwood: Maple, Ash, and Red Oak. He also used 4 species of softwood: Spruce, Northern White Cedar, Eastern Red Cedar, and Redwood. He used 4 types of preservatives. He tested 2 oil-based preservatives: creosote and pentachlorophenol (PCP). He also tested 2 water-based preservatives: chromated copper arsenate (CCA) and ammoniacal copper arsenate (ACA). He had 20 two-by-four boards of each species: of these 5 were treated with creosote, 5 with PCP, 5 with CCA, and 5 with ACA. The boards were dried and weighed then placed outdoors (all in the same experimental plot) for 10 years. At the end of 10 years, the boards were collected, dried, and re-weighed. For each board, the dry weight-loss (in grams) was recorded. The data are available in the accompanying Excel file. 1. Analyze the data as a 2-way ANOVA. Present the ANOVA table (with p -values) in a report- quality table. Source df SS MS F p species 6 33451.56871 5575.26145 26.36 <0.0001 preservative 3 7937.20029 2645.73343 12.51 <0.0001 species*preservative 18 5461.08671 303.39371 1.43 0.1293 error 112 23689.13600 211.51014 total 139 70538.99171 2. Conduct Tukey's multiple comparison procedure on the two main effects and present your results (with the means for each level) using the line method discussed in class (you may draw the lines in by hand). Spruce Maple Ash Red Oak White Cedar Redwood Red Cedar 77.910 76.280 66.325 52.290 48.585 42.900 34.980 Creosote CCA PCP ACA 66.057 59.717 57.100 45.280

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3. Give interaction plots (I recommend making these in Excel). Make 2 separate plots. One should have the species levels on the x -axis and a separate series for each preservative. The
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Lab7 - STAT 350 Lab#7 2-way ANOVA Due Friday April 4 2008...

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