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Unformatted text preview: Math 127B, Notes for lecture 11 Mrinal Raghupathi Monday, February 28th, 2011 Administrivia Today we will discuss tests of significance. Reminders 1. Homework 7 is due Thursday, 3/17 in recitation. 2. Quiz in recitation over chapter 26 on 3/17. 3. This weeks recitation will be a discussion of problems from chapter 26. 1 What is a test of significance? A test of significance is used to test a claim about a population parameter. Examples of parameters could be the average number of credit hours taken by freshmen, the average GPA and a certain university, the average rainfall in Nashville in the month of February, the amount of sugar in chocolate, or the the time taken to service a maintenance request. A test of significance involves formulating a null hypothesis, which is a claim about the popu- lation parameter. All the examples we will look at will be formulated in terms of a box model. So our null hypotheses will be claims about a box. Our data will usually indicate a suitable alternative hypothesis. We will study three tests of significance in the next three weeks. 1. Tests for averages or percentages. There are two test statistics, the z-test, and the t-test. 2. Tests for the difference of two averages. Tests like are used to determine whether two popu- lations are different. For example are high school drop-out rates different in Tennessee and Kentucky. 1 3. Tests for goodness-of-fit. The 2-test ( is the Greek letter chi, rhymes with tie) will be our focus. These tests determine whether observations fit a certain model, i.e., do the observations come from a specified box....
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