231E2F97

# 231E2F97 - Stat 231 Exam II Professor Vardeman 1 ISU...

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-1- Stat 231 Exam II October 31, 1997 Professor Vardeman 1. ISU engineering statistics students conducted a study of the properties of liquid laundry detergents. In part of their study, they measured the amount of detergent that one needs to add to 45 ml of distilled water in order to reduce surface tension to the point that a particular small shirt button floating on the surface of the water will sink. Their data for two brands and some summary statistics are below. All Brand ERA Brand 1.20, 1.05, 1.11 .85, .81, .69 1.120 .783 .075 .083 "# (a) What probability model assumptions must be made in order to do inference for the mean amount of "All" detergent that must be added in order to reduce the surface tension? (b) Based on your assumptions from (a), give a 90% lower confidence bound for the mean amount of All detergent required to reduce the surface tension. (c) Is there evidence of a difference in mean amounts of "All" and "ERA" required to reduce the surface tension of distilled water, if one is willing to run a 5% chance of committing a type I error? (Carefully SHOW all 7 steps!)

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231E2F97 - Stat 231 Exam II Professor Vardeman 1 ISU...

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