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Unformatted text preview: Making decisions based on a statistical sample ESM 206A Nov 7 2007 Environmental challenge The problem: Athington Park House is a very desirable property that was built some years before the discontinuing of lead in paint in the mid1970s. A prospective buyer is concerned about the possible presence of lead in dust contained in the house. Dust sampling offers a way of characterizing dust lead levels at a property and determining if intervention is warranted. One of the preferred methods for sampling residential dust is using baby wipes to wipe a specified surface area. A single area may be sampled using an individual wipe; or multiple areas of a room may be sampled with individual wipes, and the individual wipes combined, or composited, then submitted to the laboratory as a single sample. The EPA proposed standard stated that if dust lead levels were above 50 g/ft 2 on bare floors, a lead health hazard was possible and followup testing and/or intervention should be undertaken (40 CFR 745). Your job: Design a sampling scheme and analysis procedure such to decide whether to do intervention. Hypothesis tests of sample means Statistical theory says: If the population is normally distributed, and the population mean is , then the quantity is normally distributed with mean zero and variance one But we dont know Statistical theory also says that the quantity follows a t distribution with = n1 degrees of freedom n x /  / x X x x x t s s n  = = T DISTRIBUTION Similar to Normal Distribution Requires degrees of freedom.Requires degrees of freedom....
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This note was uploaded on 08/06/2008 for the course ESM 206 taught by Professor Kendall,berkley during the Spring '08 term at UCSB.
 Spring '08
 KENDALL,BERKLEY
 Environmental Science

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