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# Test%201%20Notes - Chapter One Introduction to Statistics...

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Chapter One – Introduction to Statistics 1.1 What is Statistics? Statistics – The science of designing studies and analyzing the data that those studies produce . Statistics is the science of learning from data . Example – Predicting an Election Using an Exit Poll Page 1 of 57

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1.2 We Learn about Populations using Samples Population – The total set of subjects in which we are interested. Ex. = the entire voting public Sample – A subset of the population for whom we have data. Ex. = 200 randomly selected voters Subject – entities that we measure in a study. Ex. = each voter in the sample Parameter – A numerical value summarizing the population data. Ex. = proportion of voters voting for candidate A in the entire population Statistic – A numerical value summarizing the sample data. Ex. = proportion of voters voting for candidate A in our sample (the 200 randomly selected voters) Page 2 of 57
Example: A college dean is interested in learning about the average age of faculty at the college. The dean takes a random sample of 30 faculty members and averages their 30 ages. Match the following: A. population B. sample C. subject D. parameter E. statistic __________________________________________ ____ the average age of all faculty members at the college ____ 30 randomly selected faculty members at the college ____ a single faculty member from the sample ____ all faculty members at the college ____ the average age of the 30 randomly selected faculty members at the college Page 3 of 57

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Symbols we use in Statistics In the previous example, we were interested in the average age of all faculty members at the University of Georgia. Whenever we are interested in an average for a full population, there is a lower-case Greek symbol we use to denote this value, µ. It is pronounced “mu”. So in this previous example, we would say µ = average age for all faculty members at UGA Now, most of the time in real life, we will not be able to actually calculate this value, so we try for the next best thing. Like in the previous example, instead of trying to find every single faculty member, we are okay with just getting an average for 30 randomly selected faculty members and use that as our estimate. Whenever we have an average calculated from a sample, like in this case, from 30 randomly selected faculty members, there is a symbol we use for that average from the sample, f8e5 x. So in this example, f8e5 x = the average age for 30 randomly selected faculty members. µ represents an average calculated from a full population. f8e5 x represents an average calculated from a sample. Page 4 of 57
More Symbols In the election example on page 1, we were interested in studying proportions, not averages. So when we are studying proportions, there are other symbols we use. If we have the proportion for an entire population, like

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## This note was uploaded on 09/10/2011 for the course STAT 2000 taught by Professor Smith during the Spring '08 term at UGA.

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Test%201%20Notes - Chapter One Introduction to Statistics...

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