VCU STAT 210 - Lecture15 (40 pages)

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Lecture15



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Lecture15

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Pages:
40
School:
Virginia Commonwealth University
Course:
Stat 210 - Basic Practice of Statistics
Basic Practice of Statistics Documents

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STAT 210 Lecture 15 Describing Relationships Between Variables September 29 2017 Test 3 Friday October 6 Covers chapter 5 pages 99 138 Combination of multiple choice questions and short answer questions and problems Formulas provided please bring calculator and writing instrument Practice Problems Pages 130 through 137 Relevant problems V 3 c V 4 c V 7 b V 9 d and V 10 c Recommended problems V 3 c V 7 b V 9 d and V 10 c Additional Reading and Examples Read pages 120 and 121 Top Hat 2 Motivating Example Watching television also often means watching or dealing with commercials and of interest is to describe the relationship between the number of hours of television watched per day and the number of commercials watched Describing Relationships To describe the relationship between two variables we must describe the direction form and strength of the relationship A scatterplot and the correlation coefficient are two statistical tools that can be used to help describe the relationship Example 26 x y 6 20 0 14 25 16 28 18 10 8 15 31 10 16 28 20 40 25 12 15 145 Sx x2 36 400 0 196 625 256 784 324 100 64 212 Sy y2 225 961 100 256 784 400 1600 625 144 225 2785 S x2 xy 90 620 0 224 700 320 1120 450 120 120 5320 S y2 3764 S xy Correlation Coefficient Sxx S x2 S x 2 n Syy S y2 S y 2 n Sxy S xy S x S y n TI 83 84 Calculator 1 First turn on diagnostics Hit 2ND and 0 bringing up the Catalog Scroll down to DiagnosticOn and hit Enter twice You only need to do this the first time 2 Enter the data into two lists say L1 and L2 3 Hit STAT then CALC and choose option 8 LinReg a bx 4 Enter the list containing the X data say L1 then comma then the list containing the Y data say L2 Hit Enter and r is the correlation coefficient Anscombe Data Page 111 As directed in class compute the correlation coefficient for the set of data you are assigned Determine the value to two decimal places You can and are encouraged to work together Data Set 1 x y Data Set 2 x y Data Set 3 x y Data Set 4 x y 10 8 13 9 11 14 6 4 12 7 5 10 8 13 9 11 14 6 4 12 7 5 10 8 13 9 11 14 6 4 12 7 5 8 8 8 8 8 8 8 19 8 8 8 8 04 6 95 7 58 8 81 8 33 9 96 7 24 4 26 10 84 4 82 5 68 9 14 8 14 8 74 8 77 9 26 8 10 6 13 3 10 9 13 7 26 4 74 7 46 6 77 12 74 7 11 7 81



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