Copyright 2011 Brooks/Cole, Cengage Learning Turning Data Into Information Use table and/or graph to represent Categorical Data Chapter 2 Class 11 1 Homework Check Assignment: Chapter 2 Exercise 2.8 and 2.11 Suggested Answer 2.8 Copyright 2011 Brooks/Cole, Cengage Learning 3 Suggested Answer 2.11 Copyright 2011 Brooks/Cole, Cengage Learning 4 5 2.3Summarizing One or Two Categorical Variables Count how many fall into each category. Calculate the percent in each category. If two variables, have the categories of the explanatory variable define the rows and compute row percentages. Numerical Summaries Copyright 2011 Brooks/Cole, Cengage Learning 6 Example 2.1 Seatbelt Use by Twelfth-Graders 2003 nationwide survey of American HS students How often do you wear a seatbelt when driving a car? Total sample size n = 3042 students. A majority, 1686/3042 =.554, or 55.4%, said they always wear a seatbelt, while 115/3042 =.038, or 3.8%, said they never wear a seatbelt. Rarely or never: 8.2% + 3.8% =12% Copyright 2011 Brooks/Cole, Cengage Learning 7 Example 2.1 Seatbelt Use by Twelfth-Graders Are females more likely to say always wear seatbelt? Are males more likely to say rarely or never wear seatbelt? Females: 915/1467 = 62.4% said always wear seatbelt Males: 771/1575 = 49.0% said always wear seatbelt. Males: 10.5% + 5.7% =16.2% rarely or never wear one. Females: 5.7% + 1.7% = 7.4% rarely or never wear one. Distribution of a Variable 8 What are the variables here? What kind of variables are they? What does it mean by distribution of a variable ? Roundoff Errors 9 Find the total number of persons and total percent Key Terminologies Distribution of a variable describes how often the possible responses occur Roundoff errors Errors in arithmetic when the numbers of a total are rounded separately 10 Pie Charts 11 Bar Graph / Bar Chart 12 Quick Check Use a pie chart and bar graph to display the following data given 13 Homework Assignment: Chapter 2 Exercise 2.27 and 2.32 Reading: Chapter 2 p