Collection of Data Statistics Class – XI2. Synopsis 1. Key terms 2. Sources of data 3. Surveys 4. Census or complete Enumeration 5. Sample survey 6. Questionnaire 7. Types of questions 8. Open ended Vs Close ended 9. Mode of data collection 10. Pilot survey 11. Methods of sampling 12. Important agencies3. Key Terms Variable: The values which change, such as production of food grains per annum, temperature of a city, etc. They are represented by the letters X,Y or Z. Observation: The value of an variable. Data: Observations corresponding to different variables. Statistical Investigation: It means search for information conducted by using statistical methods.