Pte. 1. Introduction Preliminary considerations: 1. The appeal to facts -- 2. Misuses of statistical data -- 3. Statistics in the service of science -- Pte. 2. Classification and description of mass data: 4. Classification of statistical data --5. The frecuency distribution -- 6. Methods of sumarization and description the arithmetic average -- 7. Methods of summarization and description the median and the geometric mean -- 8. Methods of summarization and description - the mode -- 9. Variation and its measurement -- 10. Index numbers - an application of statistical methods -- 11. Measures of unreliability probable error -- 12. Discovery and measurement of relationships correlation -- 13. The time series - historical statistics -- Pte. 3. The gathering and presentation of statistical data -- 14. Collection of statistical data -- 15. Presenting statistical data in tables -- 16. Graphic representation -- Apéndices