Chapter 3

# Chapter 3 - MSIT 3000 Chapter 3 Surveys and Sampling Three...

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MSIT 3000 Chapter 3 Surveys and Sampling Three Ways to Gather Data 1. Conduct an experiment 2. Take a sample, often using a survey 3. Take a census. Typically, researchers don’t have the ability to question everyone, but they don’t want their conclusions to be limited to just the people involved in the study. Generalizing from the data at hand to the world at large is something that market researchers, investors, and pollsters do every day. How is this possible? And why is it reliable? 10

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MSIT 3000 Section 3.3 Populations and Parameters Individuals, or subjects – the objects described by a set of data. Individuals may be people, but they may also be business firms, common stocks, or other objects. variable – a characteristic or property of an individual. population – the entire collection of individuals about which information is sought. sample – a subset of the individuals of a population. parameter – a quantity that describes a statistical population. statistic – a quantity that describes a statistical sample. 11
Example: A college dean is interested in learning about the average age of faculty at the college. Match the following. a. individuals b. population c. sample d. variable e. parameter f. statistic __par__ the average age of all faculty members at the college __ind__ faculty members at the college __sam__ 10 randomly selected faculty members at the college _vara___ the age of each faculty member at the college _pop___ all faculty members at the college _sta___ the average age of the 10 randomly selected faculty members at the college 12

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MSIT 3000 Section 3.4 Simple Random Sample (SRS) Sampling: The goal in sampling is to obtain individuals that will participate in a study so that accurate information about the population can be obtained. Let’s try sampling from the population of Rectangles handout. Choose any 5 rectangles you want and write down the area of each rectangle. Take the average of those rectangles and report them to me. Go ahead. I’ll wait. 13
You may think you chose at random, but people can’t be random. Choosing a sample using chance (random) reduces bias by giving all individuals an equal chance to be chosen. We need help to sample randomly this way. We can randomize by using a table of random digits, or other computer/calculator random generators. Random Digits A table of random digits is a long string of the digits 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 with these two properties: 1.Each entry in the table is equally likely to be any of the 10 digits 0 through 9. 2.The entries are independent of each other. That is, knowledge of one part of the table gives no information about any other part. 14

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## This note was uploaded on 01/10/2012 for the course MIST 3000 taught by Professor Kim during the Fall '11 term at UGA.

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Chapter 3 - MSIT 3000 Chapter 3 Surveys and Sampling Three...

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