Chapter 5 (1)

# Chapter 5(1) - Chapter 5 Experiments Good And Bad Outline Talking About Experiments How To Experiment Badly Randomized Comparative Experiments The

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Chapter 5 Experiments Good And Bad

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Outline Talking About Experiments How To Experiment Badly Randomized Comparative Experiments The Logic of Experimental Design Statistical Significance How To Live With Observational Studies

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Definitions An experiment deliberately imposes some treatment (s) on individuals in order to observe their responses. A response variable is a variable that measures an outcome or result of a study May be experimental or observational study Sometimes called the dependent variable An explanatory variable is a variable that we think “explains” or causes changes in a response variable Sometimes called the independent variable A treatment is any specific experimental condition Related to explanatory variable Usually values of the explanatory variable
Example 50 tomato plants are given fertilizer and 50 are not given fertilizer. All the plants are allowed to grow for 4 months and the total number of tomatoes weighing more than 1 oz. are counted on each plant. What is the explanatory/independent variable? A. time B. ounces C. 50 D. Whether or not given fertilizer What is the response/dependent variable? What are the treatments?

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Challenging Example 50 tomato plants are given fertilizer. Of these 25 of them are given 1 qt. of water/day and 25 are given 2 qt. of water/day. 50 tomato plants are also not given fertilizer. 25 of them are given 1 qt of water/day while 25 are given 2 qt of water/day. After 4 months, the number of tomatoes > 1 oz. are counted for each plant. Also, the plants heights are also recorded. What are the explanatory variables? What is the response variables? What are treatments? Hint: there are 4

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Motivation In a study at Nova Southeastern University, Fort Lauderdale, Florida it scientists observed that students taking courses online experience “equal learning” when compared to students taking traditional courses. Is this an experiment or an observational study?
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## This note was uploaded on 06/15/2011 for the course STAT 110 taught by Professor Johnson during the Fall '07 term at South Carolina.

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Chapter 5(1) - Chapter 5 Experiments Good And Bad Outline Talking About Experiments How To Experiment Badly Randomized Comparative Experiments The

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