STOR 155 Lecture Notes - Lecture 9: Standard Deviation, Interquartile Range, Variance

• School: UNC
• Department: Statistics And Operations Research
• Course: STOR 155
• Professor: All

Document Summary

Stor 155: introduction to statistics lecture 9: variance and standard deviation (2/5/15) Formulas for variance and standard deviation: variance = v{x, standard deviation = s. d. Variance (b a)2 / 12 (b a)2 / 24. Standard deviation (b a) / sqrt(12) (b a) / sqrt(24) Sqrt(w) / : so far, we have learned range and interquartile range that aim to describe how spread out a distribution is, review: how to calculate range, triangle 1 has parameters a=20, m=40, b=60. {x: variance and standard deviation must be positive. Example problems: a triangle has parameters of a=20, m=40, and b=60. Calculate the variance: v{x} = (b a)2 / 24, v{x} = (60 20)2 / 24, v{x} = 1600 / 24, v{x} = 66. 67. Sample variance: calculate sample variance if you do not know the parameters, two cases: have a list of a histogram s stands for sample standard deviation; s2 stands for sample variance.