1. Course on Biostatistics Part 1 What is statistics? Dr. Nicolas Padilla Raygoza Department of Nursing and Obstetrics Division of Health Sciences and Engineering Campus Celaya Salvatierra University of Guanajuato, Mexico

2. Biosketch Medical Doctor by University Autonomous of Guadalajara. Pediatrician by the Mexican Council of Certification on Pediatrics. Postgraduate Diploma on Epidemiology, London School of Hygiene and Tropical Medicine, University of London. Master Sciences with aim in Epidemiology, Atlantic International University. Doctorate Sciences with aim in Epidemiology, Atlantic International University. Professor Titular A, Full Time, University of Guanajuato. padillawarm@gmail.com raygosan@ugto.mx padillawarm@gmail.comraygosan@ugto.mx

3. Competencies The reader will describe what is statistics. He (She) will describe what is descriptive and inferential statistics. He (She) will know what are the applications of statistics.

4. Introduction Statistics The number that we obtain by count o measure things. Procedures to analyze the data. Descriptive statistics It is the methods to describe an data set. We use it to organize, to summary and to present the values of data.

5. Introduction Statistics Last, “the science and art of collecting, summarizing, and analyzing data that are subject to random variation”. It is classified into: Descriptive Inferential

6. Descriptive statistics - Examples In a cohort study on risk factors to coronary heart disease, it was measure the levels of cholesterol in blood; we can show the mean and standard deviation. Level cholesterol in blood X = 268 S ± 49

7. Descriptive statistics-Examples In a cross-sectional study in a group of children, it was determine the gender of the subjects and it was determine frequency and percentage of males and females; it can be shown in graphical form. Variablen% Sex Male Female 64 36 64 36 Total100

8. Inferential statistics It use the probability theory to obtain conclusions of a population, from data obtained in a sample. It is very hard to study all population, because of this, we study samples. Methods for estimations and hypothesis tests are important to obtain inferences.

9. Inferential statistics - Examples In a National survey on the danger of smoking, we cannot interview all population, only we can interview a sample of it. To measure prevalence of amebiasis in a population, we study a random sample. With the prevalence of the sample, we can obtain the estimate of prevalence of amebiasis in the population.

10. Applications of statistics To obtain a sample. To summary data. Make inferences of a population, based in the result of the sample. To obtain a simple model for a data set.

11. Bibliografia 1.- Last JM. A dictionary of epidemiology. New York, 4 ed. Oxford University Press, 2001:173. 2.- Kirkwood BR. Essentials of medical ststistics. Oxford, Blackwell Science, 1988: 1- 4. 3.- Altman DG. Practical statistics for medical research. Boca Ratón, Chapman & Hall/ CRC; 1991: 1-9. a