Introduce el texto aquí

Introduce el texto aquí

1. Samples

   • Parts of population
     • Sampling techniques
       • How we select members from the population to be in study

2. Observational Study

   • Observe and measure but do not modify
     • What are made?
       • Past period of time
         • Retrospective / case control study.
           • GO back in time to collect data over same past period
       • one point in time
         • Cross-Sectional study
           • Data are measured at one point in time
       • Forward in time
         • Perspective / longitudinal
           • GO forward in time and observe groups sharing common factors