Chapter-2 Collection of data
```html 📘 Chapter 2 Important Topics: Sources of data (ദത്തങ്ങളുടെ ഉറവിടങ്ങൾ), Primary vs Secondary Data (പ്രാഥമിക-ദ്വിതീയ ദത്തങ്ങൾ), Methods of collecting primary data (Personal interview, Mailing, Telephonic), Questionnaire design, Pilot Survey, Census vs Sample Survey, Random & Non-random sampling, Sampling & Non-sampling errors, National agencies (Census of India, NSSO) Primary data is first-hand information collected by the investigator. Secondary data is already collected by others and used again. Survey methods: personal interview, mailing questionnaire, telephonic interview. Census covers every unit; sample survey covers a selected group. Random sampling gives equal chance to all; non-random sampling does not. Sampling error is the difference between actual value and sample value. Chapter-2 Collection of data (ദത്ത ശേഖരണം) Introduction (ആമുഖം) In the previous chapter, you have read about what is economics. You also studie...