Chapter 3 Descriptive statistics（Numerical methods）.pptVIP

Chapter 3 Descriptive statistics Statistics in Practice [The maximum width of the skulls of ancient Egypt males] Mean value: 4000 BC ? 128.67 mm 　　　 150 AD ? 133.33 mm Dispersion: 133.33–128.67＝4.66 mm Conclusion: 1. The increase of intelligence; 　　　 2. The result of intermarriages between ancient Egyptians and people from other regions. Chapter 3 Descriptive statistics Main point 1. Central tendency and tendency of dispersion 2. Measures of location（P74~83） 3. Measures of variability（P83~89） 4. Measures of relative location and detecting outliers（P89~93） Difficulties 1. Mean； 2. Variance and standard deviation。 Chapter 3 Descriptive statistics Section 1 Central tendency and tendency of dispersion 1. Concepts 1） Central tendency: The closer to middle the variable gets, the larger the frequency is. The reverse is also true. 2） Tendency of dispersion: The tendency of deviating and dispersed at the two ends. Chapter 3 Descriptive statistics 2. The concepts of mean (average indicator) Chapter 3 Descriptive statistics 3. Types of mean Chapter 3 Descriptive statistics Section 2 Calculated average 1. Arithmetic mean (mathematical expectation, P74, 109) ※ 1) Definition: The measurement of the centre of gravity of data. [Example] Ages of 10 persons: 15, 16, 16, 17, 17, 17, 18, 18, 18, 18. What’s the average age? 2) Formulas of calculation Chapter 3 Descriptive statistics [Example] The ages of 10 persons: 15, 16, 16, 17,17, 17, 18, 18, 18, 18 ? Mean. Chapter 3 Descriptive statistics 3) Points worth noticing (1) Weight: The number to measure the importance (weights) of variables? “f or f/?f” [Example] During the “Oct. 1st”, 10 students go to different tourist site: Mt. Huang?5 persons, Mt. Wuyi?2 , Mt. Tai?2 , Mt. Laofu?1. Chapter 3 Descriptive statistics (2) The calculation of arithmetic mean of class width series [Ages of 11 persons]: 15, 17, 19, 20, 22, 22, 23, 23, 25, 26, 30. Chapter 3 Descriptive statistics (3) The mean of yes-no indicator (