Lecture 5: Data Analysis III (Relationships)Quantitative Methods 1: 1/33 ECO-10026Quantitative Methods IDr E. SymonsROOM DW1.55,DARWIN BUILDINGe-mail: [email protected]
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Lecture 5: Data Analysis III (Relationships)Quantitative Methods 1: 2/33 Lecture Contents and Objectives Data Analysis III: Relationships between Pairs of Variables Much of science/social science concerned with discovering and measuring relationships: Gravity and mass Price and demand Interest Rate and Savings Burglary rate and Unemployment Need to have measures for: Discovering relationships, Measuring strength of relationships, “Summarising” relationshipsThis lecture will consider: Relationships –linear and non-linear Scatter Diagrams Covariance Correlation Regression Equations Ref: Swift&Piff Stats 3 p425-438; Bradley (Stats) Chap 3 p 113-159
Lecture 5: Data Analysis III (Relationships)Quantitative Methods 1: 3/33 Yield and Fertilizer01020304050607080900100200300400500600700800FertilizerYieldScatter Diagrams. Visualise relationships between pairsof variables - useful starting point An Example Consider relationship between crop yield and fertilizer applications on fields. Here the experimenter has varied the fertilizer on each field… So Fertilizer is the INDEPENDENT variable (on X-axis) Yield is DEPENDENT variable (on Y-axis). Each spot shows combinationof fertilizer and yield. Seven experiments Field Fertilizer (k/hectare) Yield (tonnes/hectare) 1 100 40 2 200 50 3 300 65 4 400 70 5 500 50 6 600 65 7 700 80