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Unformatted text preview: Chapter 11 Inferences On Two Samples Fall 2008 1 Overview ● We continue with confidence intervals and hypothesis testing for more advanced models ● Models comparing two means When the two means are dependent When the two means are independent ● Models comparing two proportions Fall 2008 2 Chapter 11 Section 1 Inference about Two Means: Dependent Samples Fall 2008 3 Chapter 11 – Section 1 ● Learning objectives Distinguish between independent and dependent sampling Test claims made regarding matchedpairs data Construct and interpret confidence intervals about the population mean difference of matchedpairs data Fall 2008 4 Two Means – Dependent Samples ● Chapter 10 covered a variety of models dealing with one population The mean parameter for one population The proportion parameter for one population ● However, there are many realworld applications that need techniques to compare two populations Our Chapter 10 techniques do not do these Fall 2008 5 Two Means – Dependent Samples Examples of situations with two populations We want to test whether a certain treatment helps or not … the measurements are the “before” measurement and the “after” measurement We want to test the effectiveness of Drug A versus Drug B We give Drug A to 40 patients We give Drug B to 40 patients The measurements are the Drug A and Drug B responses Fall 2008 6 Two Means – Dependent Samples ● In certain cases, the two samples are very closely tied to each other ● A dependent sample is one when each individual in the first sample is directly matched to one individual in the second ● In certain cases, the two samples are very closely tied to each other ● A dependent sample is one when each individual in the first sample is directly matched to one individual in the second ● Examples Before and after measurements (a specific person’s before and the same person’s after) Experiments on identical twins (twins matched with each other Helpful Hint: Read Example 1 on p. 508 of your textbook. Fall 2008 7 Two Means – Dependent Samples ● On the other extreme, the two samples can be completely independent of each other ● An independent sample is when individuals selected for one sample have no relationship to the individuals selected for the other ● On the other extreme, the two samples can be completely independent of each other ● An independent sample is when individuals selected for one sample have no relationship to the individuals selected for the other ● Examples Fifty samples from one factory compared to fifty samples from another Two hundred patients divided at random into two groups of one hundred Fall 2008 8 Two Means – Dependent Samples ● The dependent samples are often called matchedpairs ● Matchedpairs is an appropriate term because each observation in sample 1 is matched to exactly one in sample 2 ● The dependent samples are often called matchedpairs...
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This note was uploaded on 02/14/2011 for the course STAT 250 taught by Professor Sims during the Spring '08 term at George Mason.
 Spring '08
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