VCU STAT 210 - Lecture3 (32 pages)

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Lecture3



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Lecture3

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Pages:
32
School:
Virginia Commonwealth University
Course:
Stat 210 - Basic Practice of Statistics
Basic Practice of Statistics Documents

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STAT 210 Lecture 3 Producing Data August 30 2017 Practice Problems Pages 38 through 42 Relevant problems II 1 and II 11 Recommended problems II 1 and II 11 Additional Reading and Examples Pages 26 through 29 Particularly read 7 on page 29 Top Hat Motivating Example It is of interest to determine what percentage of all VCU students who when asked to list three things that they enjoy doing include working out playing sport gym on their list Articles There are two articles one on pages 11 through 14 and one on pages 15 and 16 Read the article on pages 15 and 16 of the Supplement and answer the three clicker questions related to this Top Hat 3 Articles Outside of class read the article on pages 11 14 and think about the population of interest the sample and any parameters and statistics Producing Data To perform any type of statistical analysis or statistical inference we need data How do we get this data Sampling Procedures We select a sample of the population and only measure or contact the subjects in the sample Experimental Designs A treatment is imposed on the experimental units or subjects and a response is observed You then can compare the effect that the treatment is having on the response A Sampling Designs A population is a large set of subjects that the researcher wants to make statements about Example all VCU students The problem is that in many cases time cost or inconvenience make it impossible to contact or measure every member of the population A Sampling Designs Instead we obtain a representative sample of the population and use the data in the sample to make inferences about the population Example We can easily contact a sample of 200 VCU students Representative Sample The sample should be as representative of the population as possible meaning that the characteristics of the sample should mimic the characteristics of the population Example If the population is 60 female then the sample should be roughly 60 female as well if we think a person s sex will influence the response Bias Bias exists when some subjects or outcomes are systematically favored over others A sample which is representative of the population should be free of bias If the sample is not representative then the results will be biased in favor of the responses of those which are overrepresented Selection Bias Selection bias occurs when one or more types of subjects are systematically excluded from the sample Selection Bias Selection bias occurs when one or more types of subjects are systematically excluded from the sample Example Suppose the population consists of all students at this university and of interest is the opinion of students regarding an increase in student fees to pay for an expansion of the basketball arena Contacting all students for their opinions is not possible so instead a sample of 200 students in attendance at a basketball game is selected and they are asked their



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