VCU STAT 210 - Lecture7 (67 pages)

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Lecture7



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Lecture7

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Pages:
67
School:
Virginia Commonwealth University
Course:
Stat 210 - Basic Practice of Statistics
Basic Practice of Statistics Documents
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STAT 210 Lecture 7 III Graphically Displaying Distributions September 11 2017 Practice Problems Pages 65 through 68 Relevant problems III 1 III 3 III 7 III 11 III 12 and III 13 a only Recommended problems III 1 III 5 and III 13 a The use the plot to describe the distribution part of the problems can be postponed until after Friday s class Additional Reading and Examples Read pages 61 and 62 Top Hat Motivating Example see page 44 Many college students enjoy playing video games and a study was created to estimate what percentage of all students at this university who include playing video games on their list of top three things to do For those who play video games it is also of interest to estimate the typical cost of the video games and to describe the distribution of video game costs As described what is the population of interest for this example Motivating Example Many college students enjoy playing video games and a study was created to estimate what percentage of all students at this university who include playing video games on their list of top three things to do For those who play video games it is also of interest to estimate the typical cost of the video games and to describe the distribution of video game costs As described what is the population of interest for this example All students at this university Motivating Example Many college students enjoy playing video games and a study was created to estimate what percentage of all students at this university who include playing video games on their list of top three things to do For those who play video games it is also of interest to estimate the typical cost of the video games and to describe the distribution of video game costs What type of characteristic is percentage of all students at this university who include playing video games on their list of top three things to do Motivating Example Many college students enjoy playing video games and a study was created to estimate what percentage of all students at this university who include playing video games on their list of top three things to do For those who play video games it is also of interest to estimate the typical cost of the video games and to describe the distribution of video game costs What type of characteristic is percentage of all students at this university who include playing video games on their list of top three things to do A percentage is calculated so it is a continuous quantitative variable Motivating Example Many college students enjoy playing video games and a study was created to estimate what percentage of all students at this university who include playing video games on their list of top three things to do For those who play video games it is also of interest to estimate the typical cost of the video games and to describe the distribution of video game costs What type of characteristic is cost of video games to the nearest dollar and cent for example 40 95 Motivating Example Many college students enjoy playing video games and a study was created to estimate what percentage of all students at this university who include playing video games on their list of top three things to do For those who play video games it is also of interest to estimate the typical cost of the video games and to describe the distribution of video game costs What type of characteristic is cost of video games to the nearest dollar and cent for example 40 95 One can count cents pennies so it is a discrete quantitative variable Motivating Example Many college students enjoy playing video games and a study was created to estimate what percentage of all students at this university who include playing video games on their list of top three things to do For those who play video games it is also of interest to estimate the typical cost of the video games and to describe the distribution of video game costs In a sample of 121 students at this university 10 included video games on their list of top three things to do Hence 10 121 8 3 of the students in this sample included video games on their list Is 8 3 an example of a parameter or a statistic Motivating Example Many college students enjoy playing video games and a study was created to estimate what percentage of all students at this university who include playing video games on their list of top three things to do For those who play video games it is also of interest to estimate the typical cost of the video games and to describe the distribution of video game costs In a sample of 121 students at this university 10 included video games on their list of top three things to do Hence 10 121 8 3 of the students in this sample included video games on their list Is 8 3 an example of a parameter or a statistic Statistic because it is computed from the sample data Motivating Example Many college students enjoy playing video games and a study was created to estimate what percentage of all students at this university who include playing video games on their list of top three things to do For those who play video games it is also of interest to estimate the typical cost of the video games and to describe the distribution of video game costs The cost of the last video game that was purchased by a sample of 20 students is given below This data will be used in later sections of this chapter 59 95 35 99 41 29 38 99 45 39 24 95 29 59 32 95 40 50 47 85 30 99 52 95 25 50 44 45 47 99 34 85 32 00 26 99 48 59 53 29 Descriptive Statistics The branch of statistics concerned with numerical and graphical techniques for analyzing and describing one or more characteristics of a population and for comparing characteristics among populations Descriptive Statistics When describing a distribution we usually describe four things 1 the center of the distribution 2 the spread or dispersion or variability of the distribution 3 the shape of the distribution 4 any unusual features in the distribution Top Hat Purpose of Graphical Procedures 1 Simplify the data 2 Make it easy to describe distributions 3 Make it easy to make statistical inferences Qualitative Variables Variables whose measurement vary in name or kind only and cannot be ranked in any order of magnitude Pie charts Bar graphs Quantitative Variables Variables in which measurements vary in magnitude from trial to trial meaning some order or ranking can be applied Possible measurements are divided into class intervals Each measurement should fall in one and exactly one interval Example Bad 0 10 11 16


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