1. AP Statistics HW: p.48-52 #39, 43,44, 45 Lab due next class Obj: to use variance and standard deviation Do Now: 1.Make a modified box plot for the # of home runs hit by Babe Ruth in each of his seasons as a Yankee: 54, 59, 35, 41, 46, 25, 47, 60, 54, 46, 49, 46, 41, 34, 22 2.Give the “five-number summary” for this data set. 3.Type the data into L 1 and use the calculator to make a modified box plot. C 1, D 8

2. Standard Deviation Give a numerical value to the spread of a distribution –If you give mean as the center, give standard deviation as the spread. –If you give the median as the center, give range as the spread. To calculate std. dev. you must first calculate variance.

3. Variance Notation: s 2 For a data set with mean = and n observations: x 1, x 2, …, x n

4. Standard Deviation (s) s = –Measures the spread about the mean, so should only be used when the mean is given as the measure of center. –(Handout of formulas)

5. SOCS For a strongly skewed distribution, the five-number summary is better to describe center and spread. Mean and standard deviation are better for symmetric distributions. (Why?) For strongly skewed distributions, very high or very low values can greatly affect the mean and standard deviation. *** Always plot your data first!!! ***

6. Try Page 52 # 40 Compare your answers with your partner