2 1 Describing Location in a Distribution Day

2. 1 – Describing Location in a Distribution Day 1 on Assignment Guide

Percentiles • The percent of observations in a set of data that are below a certain value. • It is possible to include equal to, but we will strictly do below for consistency

Cumulative Relative Frequency Plot • Remember relative frequency is percent • Cumulative – running total AKA “Ogives”

Shape for Cumulative Relative Frequency Plot Where is the graph the steepest? What does this mean? Sketch a Cumulative Relative Frequency Plot for this data. Describe the shape. Sketch a Cumulative Relative Frequency Plot for symmetric and skewed left

Check Your Understanding Turn to page 89 and do problems 1 – 4 We will do one at a time on the whiteboards

z-scores • Also called standardized value • It is unit-less • Tells us how many standard deviations away from the mean a particular value is • Formula is on your formula sheet and on p. 90

In 2009, the mean number of wins in MLB was 81 with a standard deviation of 11. 4 wins. 1. Find and interpret the z-score for the NY Yankees if they had 103 wins. 2. Find and interpret the z-score for the NY Mets if they had 70 wins. 1. z-score = (103 -81)/11. 4 = 1. 93. Interpret: The NY Yankees were 1. 93 standard deviations above the mean number of wins. 2. z-score = (70 -81)/11. 4 = -0. 96. Interpret: The NY Mets were 0. 96 standard deviations below the mean number of wins.