1. Copyright (C) 2002 Houghton Mifflin Company. All rights reserved. 1 Statistics is The study of how to: collect organize analyze interpret numerical information from data

2. Copyright (C) 2002 Houghton Mifflin Company. All rights reserved. 2 Individuals and Variables Individual: a person or object included in a study Variable: a characteristic of the individual to be measured or observed

3. Copyright (C) 2002 Houghton Mifflin Company. All rights reserved. 3 Quantitative and Qualitative Data Quantitative variable has a value or numerical measurement –example: number of siblings Qualitative variable places an individual in a category or group –example: brand of computer

4. Copyright (C) 2002 Houghton Mifflin Company. All rights reserved. 4 Population Variable is taken from every individual of interest Example: incomes of all residents of a county

5. Copyright (C) 2002 Houghton Mifflin Company. All rights reserved. 5 Sample Variable is taken from only some of the individuals Example: incomes of selected residents

6. Copyright (C) 2002 Houghton Mifflin Company. All rights reserved. 6 Levels of Measurement Nominal Ordinal Interval Ratio

7. Copyright (C) 2002 Houghton Mifflin Company. All rights reserved. 7 Nominal Measurement Data is put into categories only. Example: eye color

8. Copyright (C) 2002 Houghton Mifflin Company. All rights reserved. 8 Ordinal Measurement Data can be ordered. Differences cannot be calculated or interpreted. Example: class rank

9. Copyright (C) 2002 Houghton Mifflin Company. All rights reserved. 9 Interval Measurement Data can be ordered. Differences between data values can be compared. Example: temperature

10. Copyright (C) 2002 Houghton Mifflin Company. All rights reserved. 10 Ratio Measurement Data can be ordered. Differences and ratios between data values can be compared. Example: time

11. Copyright (C) 2002 Houghton Mifflin Company. All rights reserved. 11 Branches of Statistics Descriptive: methods of organizing, picturing, and summarizing information Inferential: methods of using information from a sample to draw conclusions regarding the population