AF Chaper 7 handouts FA08

AF Chaper 7 handouts FA08 - The Process of a Statistical...

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1 STAT 2000 Chapter 7 C fid I t l Confidence Intervals Agresti-Franklin Identify Objective Question(s) about a population Design Study and Collect Data Select a sample from a population Make Inferences The Process of a Statistical Study Describe Data Organize and present sampledata about a population Make predictions and draw conclusions Principles of Probability As we begin to talk about Inference, let’s look back at what we have done before, and why. Gathering Data – Statistical inference methods assume that data was collected with some type of randomization. Sampling Distributions – Probability calculations Sampling Distributions Probability calculations used in inference refer to sampling distributions. Two types of Inference Estimation – Chapter 7 Hypothesis Testing – Chapters 8-9 A point estimate of a population parameter is an estimate given by a single value. Sample Statistics are point estimates of Population Parameters. Sample Population Statistic Parameter Mean μ Standard Deviation s σ Proportion p x ˆ p An interval estimate of a population parameter is given by two values between which we expect to have the population parameter. (Why would we want an interval estimate instead of a point estimate?) Our interval estimate is given by point estimate ± margin of error The margin of error is how much we expect to be *off*. SAMPLE: Interviews with 706 likely voters, conducted by telephone on July 9-11, 2004. MARGIN OF ERROR: ± 4% The point estimate of the proportion that would vote for Bush was 0.46. The interval estimate would be 0.46 ± 0.04, and we would write this as (0.42, 0.50). The lower limit is 0.42, and the upper limit is 0.50.
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